enmi-conf.org: comparison wp/wp-includes/taxonomy.php

equal deleted inserted replaced

-:490d5cc509ed
+:cf61fcea0001
 <?php
 /**
-* Taxonomy API
+* Core Taxonomy API
 *
 * @package WordPress
 * @subpackage Taxonomy
-* @since 2.3.0
 */
 //
 // Taxonomy Registration
 //
 /**
 * Creates the initial taxonomies.
 *
 * This function fires twice: in wp-settings.php before plugins are loaded (for
-* backwards compatibility reasons), and again on the 'init' action. We must avoid
+* backward compatibility reasons), and again on the {@see 'init'} action. We must
-* registering rewrite rules before the 'init' action.
+* avoid registering rewrite rules before the {@see 'init'} action.
+*
+* @since 2.8.0
+*
+* @global WP_Rewrite $wp_rewrite The WordPress rewrite class.
 */
 function create_initial_taxonomies() {
 	global $wp_rewrite;
 	if ( ! did_action( 'init' ) ) {
 		$rewrite = array( 'category' => false, 'post_tag' => false, 'post_format' => false );
 	} else {
 		/**
-		 * Filter the post formats rewrite base.
+		 * Filters the post formats rewrite base.
 		 *
 		 * @since 3.1.0
 		 *
 		 * @param string $context Context of the rewrite base. Default 'type'.
 		 */
 		'rewrite' => $rewrite['category'],
 		'public' => true,
 		'show_ui' => true,
 		'show_admin_column' => true,
 		'_builtin' => true,
+		'capabilities' => array(
+			'manage_terms' => 'manage_categories',
+			'edit_terms'   => 'edit_categories',
+			'delete_terms' => 'delete_categories',
+			'assign_terms' => 'assign_categories',
+		),
+		'show_in_rest' => true,
+		'rest_base' => 'categories',
+		'rest_controller_class' => 'WP_REST_Terms_Controller',
 	) );
 	register_taxonomy( 'post_tag', 'post', array(
 	 	'hierarchical' => false,
 		'query_var' => 'tag',
 		'rewrite' => $rewrite['post_tag'],
 		'public' => true,
 		'show_ui' => true,
 		'show_admin_column' => true,
 		'_builtin' => true,
+		'capabilities' => array(
+			'manage_terms' => 'manage_post_tags',
+			'edit_terms'   => 'edit_post_tags',
+			'delete_terms' => 'delete_post_tags',
+			'assign_terms' => 'assign_post_tags',
+		),
+		'show_in_rest' => true,
+		'rest_base' => 'tags',
+		'rest_controller_class' => 'WP_REST_Terms_Controller',
 	) );
 	register_taxonomy( 'nav_menu', 'nav_menu_item', array(
 		'public' => false,
 		'hierarchical' => false,
 			'add_new_item' => __( 'Add New Link Category' ),
 			'new_item_name' => __( 'New Link Category Name' ),
 			'separate_items_with_commas' => null,
 			'add_or_remove_items' => null,
 			'choose_from_most_used' => null,
+			'back_to_items' => __( '&larr; Back to Link Categories' ),
 		),
 		'capabilities' => array(
 			'manage_terms' => 'manage_links',
 			'edit_terms'   => 'manage_links',
 			'delete_terms' => 'manage_links',
 			'assign_terms' => 'manage_links',
 		),
 		'query_var' => false,
 		'rewrite' => false,
 		'public' => false,
-		'show_ui' => false,
+		'show_ui' => true,
 		'_builtin' => true,
 	) );
 	register_taxonomy( 'post_format', 'post', array(
 		'public' => true,
 		'show_in_nav_menus' => current_theme_supports( 'post-formats' ),
 	) );
 }
 /**
-* Get a list of registered taxonomy objects.
+* Retrieves a list of registered taxonomy names or objects.
 *
 * @since 3.0.0
-* @uses $wp_taxonomies
+*
-*
+* @global array $wp_taxonomies The registered taxonomies.
-* @param array $args An array of key => value arguments to match against the taxonomy objects.
+*
-* @param string $output The type of output to return, either taxonomy 'names' or 'objects'. 'names' is the default.
+* @param array  $args     Optional. An array of `key => value` arguments to match against the taxonomy objects.
-* @param string $operator The logical operation to perform. 'or' means only one element
+*                         Default empty array.
-*  from the array needs to match; 'and' means all elements must match. The default is 'and'.
+* @param string $output   Optional. The type of output to return in the array. Accepts either taxonomy 'names'
-* @return array A list of taxonomy names or objects
+*                         or 'objects'. Default 'names'.
+* @param string $operator Optional. The logical operation to perform. Accepts 'and' or 'or'. 'or' means only
+*                         one element from the array needs to match; 'and' means all elements must match.
+*                         Default 'and'.
+* @return array A list of taxonomy names or objects.
 */
 function get_taxonomies( $args = array(), $output = 'names', $operator = 'and' ) {
 	global $wp_taxonomies;
 	$field = ('names' == $output) ? 'name' : false;
 	return wp_filter_object_list($wp_taxonomies, $args, $operator, $field);
 }
 /**
-* Return all of the taxonomy names that are of $object_type.
+* Return the names or objects of the taxonomies which are registered for the requested object or object type, such as
-*
+* a post object or post type name.
-* It appears that this function can be used to find all of the names inside of
+*
-* $wp_taxonomies global variable.
+* Example:
 *
-* `<?php $taxonomies = get_object_taxonomies('post'); ?>` Should
+*     $taxonomies = get_object_taxonomies( 'post' );
-* result in `Array( 'category', 'post_tag' )`
+*
+* This results in:
+*
+*     Array( 'category', 'post_tag' )
 *
 * @since 2.3.0
 *
-* @uses $wp_taxonomies
+* @global array $wp_taxonomies The registered taxonomies.
 *
-* @param array|string|object $object Name of the type of taxonomy object, or an object (row from posts)
+* @param array|string|WP_Post $object Name of the type of taxonomy object, or an object (row from posts)
-* @param string $output The type of output to return, either taxonomy 'names' or 'objects'. 'names' is the default.
+* @param string               $output Optional. The type of output to return in the array. Accepts either
+*                                     taxonomy 'names' or 'objects'. Default 'names'.
 * @return array The names of all taxonomy of $object_type.
 */
-function get_object_taxonomies($object, $output = 'names') {
+function get_object_taxonomies( $object, $output = 'names' ) {
 	global $wp_taxonomies;
 	if ( is_object($object) ) {
 		if ( $object->post_type == 'attachment' )
-			return get_attachment_taxonomies($object);
+			return get_attachment_taxonomies( $object, $output );
 		$object = $object->post_type;
 	}
 	$object = (array) $object;
 * The get_taxonomy function will first check that the parameter string given
 * is a taxonomy object and if it is, it will return it.
 *
 * @since 2.3.0
 *
-* @uses $wp_taxonomies
+* @global array $wp_taxonomies The registered taxonomies.
 *
-* @param string $taxonomy Name of taxonomy object to return
+* @param string $taxonomy Name of taxonomy object to return.
-* @return object|bool The Taxonomy Object or false if $taxonomy doesn't exist
+* @return WP_Taxonomy|false The Taxonomy Object or false if $taxonomy doesn't exist.
 */
 function get_taxonomy( $taxonomy ) {
 	global $wp_taxonomies;
 	if ( ! taxonomy_exists( $taxonomy ) )
 *
 * Formerly is_taxonomy(), introduced in 2.3.0.
 *
 * @since 3.0.0
 *
-* @uses $wp_taxonomies
+* @global array $wp_taxonomies The registered taxonomies.
 *
-* @param string $taxonomy Name of taxonomy object
+* @param string $taxonomy Name of taxonomy object.
 * @return bool Whether the taxonomy exists.
 */
 function taxonomy_exists( $taxonomy ) {
 	global $wp_taxonomies;
 *
 * A false return value might also mean that the taxonomy does not exist.
 *
 * @since 2.3.0
 *
-* @param string $taxonomy Name of taxonomy object
+* @param string $taxonomy Name of taxonomy object.
-* @return bool Whether the taxonomy is hierarchical
+* @return bool Whether the taxonomy is hierarchical.
 */
 function is_taxonomy_hierarchical($taxonomy) {
 	if ( ! taxonomy_exists($taxonomy) )
 		return false;
 	$taxonomy = get_taxonomy($taxonomy);
 	return $taxonomy->hierarchical;
 }
 /**
-* Create or modify a taxonomy object. Do not use before init.
+* Creates or modifies a taxonomy object.
 *
-* A simple function for creating or modifying a taxonomy object based on the
+* Note: Do not use before the {@see 'init'} hook.
-* parameters given. The function will accept an array (third optional
+*
-* parameter), along with strings for the taxonomy name and another string for
+* A simple function for creating or modifying a taxonomy object based on
-* the object type.
+* the parameters given. If modifying an existing taxonomy object, note
-*
+* that the `$object_type` value from the original registration will be
-* Nothing is returned, so expect error maybe or use taxonomy_exists() to check
+* overwritten.
-* whether taxonomy exists.
-*
-* Optional $args contents:
-*
-* - label - Name of the taxonomy shown in the menu. Usually plural. If not set, labels['name'] will be used.
-* - labels - An array of labels for this taxonomy.
-*     * By default tag labels are used for non-hierarchical types and category labels for hierarchical ones.
-*     * You can see accepted values in {@link get_taxonomy_labels()}.
-* - description - A short descriptive summary of what the taxonomy is for. Defaults to blank.
-* - public - If the taxonomy should be publicly queryable; //@TODO not implemented.
-*     * Defaults to true.
-* - hierarchical - Whether the taxonomy is hierarchical (e.g. category). Defaults to false.
-* - show_ui - Whether to generate a default UI for managing this taxonomy in the admin.
-*     * If not set, the default is inherited from public.
-* - show_in_menu - Whether to show the taxonomy in the admin menu.
-*     * If true, the taxonomy is shown as a submenu of the object type menu.
-*     * If false, no menu is shown.
-*     * show_ui must be true.
-*     * If not set, the default is inherited from show_ui.
-* - show_in_nav_menus - Makes this taxonomy available for selection in navigation menus.
-*     * If not set, the default is inherited from public.
-* - show_tagcloud - Whether to list the taxonomy in the Tag Cloud Widget.
-*     * If not set, the default is inherited from show_ui.
-* - show_in_quick_edit - Whether to show the taxonomy in the quick/bulk edit panel.
-*     * It not set, the default is inherited from show_ui.
-* - show_admin_column - Whether to display a column for the taxonomy on its post type listing screens.
-*     * Defaults to false.
-* - meta_box_cb - Provide a callback function for the meta box display.
-*     * If not set, defaults to post_categories_meta_box for hierarchical taxonomies
-*     and post_tags_meta_box for non-hierarchical.
-*     * If false, no meta box is shown.
-* - capabilities - Array of capabilities for this taxonomy.
-*     * You can see accepted values in this function.
-* - rewrite - Triggers the handling of rewrites for this taxonomy. Defaults to true, using $taxonomy as slug.
-*     * To prevent rewrite, set to false.
-*     * To specify rewrite rules, an array can be passed with any of these keys
-*         * 'slug' => string Customize the permastruct slug. Defaults to $taxonomy key
-*         * 'with_front' => bool Should the permastruct be prepended with WP_Rewrite::$front. Defaults to true.
-*         * 'hierarchical' => bool Either hierarchical rewrite tag or not. Defaults to false.
-*         * 'ep_mask' => const Assign an endpoint mask.
-*             * If not specified, defaults to EP_NONE.
-* - query_var - Sets the query_var key for this taxonomy. Defaults to $taxonomy key
-*     * If false, a taxonomy cannot be loaded at ?{query_var}={term_slug}
-*     * If specified as a string, the query ?{query_var_string}={term_slug} will be valid.
-* - update_count_callback - Works much like a hook, in that it will be called when the count is updated.
-*     * Defaults to _update_post_term_count() for taxonomies attached to post types, which then confirms
-*       that the objects are published before counting them.
-*     * Defaults to _update_generic_term_count() for taxonomies attached to other object types, such as links.
-* - _builtin - true if this taxonomy is a native or "built-in" taxonomy. THIS IS FOR INTERNAL USE ONLY!
 *
 * @since 2.3.0
 * @since 4.2.0 Introduced `show_in_quick_edit` argument.
+* @since 4.4.0 The `show_ui` argument is now enforced on the term editing screen.
+* @since 4.4.0 The `public` argument now controls whether the taxonomy can be queried on the front end.
+* @since 4.5.0 Introduced `publicly_queryable` argument.
+* @since 4.7.0 Introduced `show_in_rest`, 'rest_base' and 'rest_controller_class'
+*              arguments to register the Taxonomy in REST API.
 *
 * @global array $wp_taxonomies Registered taxonomies.
-* @global WP    $wp            WP instance.
+*
-*
+* @param string       $taxonomy    Taxonomy key, must not exceed 32 characters.
-* @param string $taxonomy Taxonomy key, must not exceed 32 characters.
+* @param array|string $object_type Object type or array of object types with which the taxonomy should be associated.
-* @param array|string $object_type Name of the object type for the taxonomy object.
+* @param array|string $args        {
-* @param array|string $args See optional args description above.
+*     Optional. Array or query string of arguments for registering a taxonomy.
-* @return null|WP_Error WP_Error if errors, otherwise null.
+*
+*     @type array         $labels                An array of labels for this taxonomy. By default, Tag labels are
+*                                                used for non-hierarchical taxonomies, and Category labels are used
+*                                                for hierarchical taxonomies. See accepted values in
+*                                                get_taxonomy_labels(). Default empty array.
+*     @type string        $description           A short descriptive summary of what the taxonomy is for. Default empty.
+*     @type bool          $public                Whether a taxonomy is intended for use publicly either via
+*                                                the admin interface or by front-end users. The default settings
+*                                                of `$publicly_queryable`, `$show_ui`, and `$show_in_nav_menus`
+*                                                are inherited from `$public`.
+*     @type bool          $publicly_queryable    Whether the taxonomy is publicly queryable.
+*                                                If not set, the default is inherited from `$public`
+*     @type bool          $hierarchical          Whether the taxonomy is hierarchical. Default false.
+*     @type bool          $show_ui               Whether to generate and allow a UI for managing terms in this taxonomy in
+*                                                the admin. If not set, the default is inherited from `$public`
+*                                                (default true).
+*     @type bool          $show_in_menu          Whether to show the taxonomy in the admin menu. If true, the taxonomy is
+*                                                shown as a submenu of the object type menu. If false, no menu is shown.
+*                                                `$show_ui` must be true. If not set, default is inherited from `$show_ui`
+*                                                (default true).
+*     @type bool          $show_in_nav_menus     Makes this taxonomy available for selection in navigation menus. If not
+*                                                set, the default is inherited from `$public` (default true).
+*     @type bool          $show_in_rest          Whether to include the taxonomy in the REST API.
+*     @type string        $rest_base             To change the base url of REST API route. Default is $taxonomy.
+*     @type string        $rest_controller_class REST API Controller class name. Default is 'WP_REST_Terms_Controller'.
+*     @type bool          $show_tagcloud         Whether to list the taxonomy in the Tag Cloud Widget controls. If not set,
+*                                                the default is inherited from `$show_ui` (default true).
+*     @type bool          $show_in_quick_edit    Whether to show the taxonomy in the quick/bulk edit panel. It not set,
+*                                                the default is inherited from `$show_ui` (default true).
+*     @type bool          $show_admin_column     Whether to display a column for the taxonomy on its post type listing
+*                                                screens. Default false.
+*     @type bool|callable $meta_box_cb           Provide a callback function for the meta box display. If not set,
+*                                                post_categories_meta_box() is used for hierarchical taxonomies, and
+*                                                post_tags_meta_box() is used for non-hierarchical. If false, no meta
+*                                                box is shown.
+*     @type array         $capabilities {
+*         Array of capabilities for this taxonomy.
+*
+*         @type string $manage_terms Default 'manage_categories'.
+*         @type string $edit_terms   Default 'manage_categories'.
+*         @type string $delete_terms Default 'manage_categories'.
+*         @type string $assign_terms Default 'edit_posts'.
+*     }
+*     @type bool|array    $rewrite {
+*         Triggers the handling of rewrites for this taxonomy. Default true, using $taxonomy as slug. To prevent
+*         rewrite, set to false. To specify rewrite rules, an array can be passed with any of these keys:
+*
+*         @type string $slug         Customize the permastruct slug. Default `$taxonomy` key.
+*         @type bool   $with_front   Should the permastruct be prepended with WP_Rewrite::$front. Default true.
+*         @type bool   $hierarchical Either hierarchical rewrite tag or not. Default false.
+*         @type int    $ep_mask      Assign an endpoint mask. Default `EP_NONE`.
+*     }
+*     @type string        $query_var             Sets the query var key for this taxonomy. Default `$taxonomy` key. If
+*                                                false, a taxonomy cannot be loaded at `?{query_var}={term_slug}`. If a
+*                                                string, the query `?{query_var}={term_slug}` will be valid.
+*     @type callable      $update_count_callback Works much like a hook, in that it will be called when the count is
+*                                                updated. Default _update_post_term_count() for taxonomies attached
+*                                                to post types, which confirms that the objects are published before
+*                                                counting them. Default _update_generic_term_count() for taxonomies
+*                                                attached to other object types, such as users.
+*     @type bool          $_builtin              This taxonomy is a "built-in" taxonomy. INTERNAL USE ONLY!
+*                                                Default false.
+* }
+* @return WP_Error|void WP_Error, if errors.
 */
 function register_taxonomy( $taxonomy, $object_type, $args = array() ) {
-	global $wp_taxonomies, $wp;
+	global $wp_taxonomies;
 	if ( ! is_array( $wp_taxonomies ) )
 		$wp_taxonomies = array();
-	$defaults = array(
+	$args = wp_parse_args( $args );
-		'labels'                => array(),
-		'description'           => '',
-		'public'                => true,
-		'hierarchical'          => false,
-		'show_ui'               => null,
-		'show_in_menu'          => null,
-		'show_in_nav_menus'     => null,
-		'show_tagcloud'         => null,
-		'show_in_quick_edit'	=> null,
-		'show_admin_column'     => false,
-		'meta_box_cb'           => null,
-		'capabilities'          => array(),
-		'rewrite'               => true,
-		'query_var'             => $taxonomy,
-		'update_count_callback' => '',
-		'_builtin'              => false,
-	);
-	$args = wp_parse_args( $args, $defaults );
 	if ( empty( $taxonomy ) || strlen( $taxonomy ) > 32 ) {
-		_doing_it_wrong( __FUNCTION__, __( 'Taxonomy names must be between 1 and 32 characters in length.' ), '4.2' );
+		_doing_it_wrong( __FUNCTION__, __( 'Taxonomy names must be between 1 and 32 characters in length.' ), '4.2.0' );
 		return new WP_Error( 'taxonomy_length_invalid', __( 'Taxonomy names must be between 1 and 32 characters in length.' ) );
 	}
-	if ( false !== $args['query_var'] && ! empty( $wp ) ) {
+	$taxonomy_object = new WP_Taxonomy( $taxonomy, $object_type, $args );
-		if ( true === $args['query_var'] )
+	$taxonomy_object->add_rewrite_rules();
-			$args['query_var'] = $taxonomy;
-		else
+	$wp_taxonomies[ $taxonomy ] = $taxonomy_object;
-			$args['query_var'] = sanitize_title_with_dashes( $args['query_var'] );
-		$wp->add_query_var( $args['query_var'] );
+	$taxonomy_object->add_hooks();
-	}
-	if ( false !== $args['rewrite'] && ( is_admin() || '' != get_option( 'permalink_structure' ) ) ) {
-		$args['rewrite'] = wp_parse_args( $args['rewrite'], array(
-			'with_front' => true,
-			'hierarchical' => false,
-			'ep_mask' => EP_NONE,
-		) );
-		if ( empty( $args['rewrite']['slug'] ) )
-			$args['rewrite']['slug'] = sanitize_title_with_dashes( $taxonomy );
-		if ( $args['hierarchical'] && $args['rewrite']['hierarchical'] )
-			$tag = '(.+?)';
-		else
-			$tag = '([^/]+)';
-		add_rewrite_tag( "%$taxonomy%", $tag, $args['query_var'] ? "{$args['query_var']}=" : "taxonomy=$taxonomy&term=" );
-		add_permastruct( $taxonomy, "{$args['rewrite']['slug']}/%$taxonomy%", $args['rewrite'] );
-	}
-	// If not set, default to the setting for public.
-	if ( null === $args['show_ui'] )
-		$args['show_ui'] = $args['public'];
-	// If not set, default to the setting for show_ui.
-	if ( null === $args['show_in_menu' ] || ! $args['show_ui'] )
-		$args['show_in_menu' ] = $args['show_ui'];
-	// If not set, default to the setting for public.
-	if ( null === $args['show_in_nav_menus'] )
-		$args['show_in_nav_menus'] = $args['public'];
-	// If not set, default to the setting for show_ui.
-	if ( null === $args['show_tagcloud'] )
-		$args['show_tagcloud'] = $args['show_ui'];
-	// If not set, default to the setting for show_ui.
-	if ( null === $args['show_in_quick_edit'] ) {
-		$args['show_in_quick_edit'] = $args['show_ui'];
-	}
-	$default_caps = array(
-		'manage_terms' => 'manage_categories',
-		'edit_terms'   => 'manage_categories',
-		'delete_terms' => 'manage_categories',
-		'assign_terms' => 'edit_posts',
-	);
-	$args['cap'] = (object) array_merge( $default_caps, $args['capabilities'] );
-	unset( $args['capabilities'] );
-	$args['name'] = $taxonomy;
-	$args['object_type'] = array_unique( (array) $object_type );
-	$args['labels'] = get_taxonomy_labels( (object) $args );
-	$args['label'] = $args['labels']->name;
-	// If not set, use the default meta box
-	if ( null === $args['meta_box_cb'] ) {
-		if ( $args['hierarchical'] )
-			$args['meta_box_cb'] = 'post_categories_meta_box';
-		else
-			$args['meta_box_cb'] = 'post_tags_meta_box';
-	}
-	$wp_taxonomies[ $taxonomy ] = (object) $args;
-	// register callback handling for metabox
-	add_filter( 'wp_ajax_add-' . $taxonomy, '_wp_ajax_add_hierarchical_term' );
 	/**
 	 * Fires after a taxonomy is registered.
 	 *
 	 * @since 3.3.0
 	 *
 	 * @param string       $taxonomy    Taxonomy slug.
 	 * @param array|string $object_type Object type or array of object types.
 	 * @param array        $args        Array of taxonomy registration arguments.
 	 */
-	do_action( 'registered_taxonomy', $taxonomy, $object_type, $args );
+	do_action( 'registered_taxonomy', $taxonomy, $object_type, (array) $taxonomy_object );
 }
 /**
-* Builds an object with all taxonomy labels out of a taxonomy object
+* Unregisters a taxonomy.
 *
-* Accepted keys of the label array in the taxonomy object:
+* Can not be used to unregister built-in taxonomies.
 *
-* - name - general name for the taxonomy, usually plural. The same as and overridden by $tax->label. Default is Tags/Categories
+* @since 4.5.0
-* - singular_name - name for one object of this taxonomy. Default is Tag/Category
+*
-* - search_items - Default is Search Tags/Search Categories
+* @global WP    $wp            Current WordPress environment instance.
-* - popular_items - This string isn't used on hierarchical taxonomies. Default is Popular Tags
+* @global array $wp_taxonomies List of taxonomies.
-* - all_items - Default is All Tags/All Categories
+*
-* - parent_item - This string isn't used on non-hierarchical taxonomies. In hierarchical ones the default is Parent Category
+* @param string $taxonomy Taxonomy name.
-* - parent_item_colon - The same as `parent_item`, but with colon `:` in the end
+* @return bool|WP_Error True on success, WP_Error on failure or if the taxonomy doesn't exist.
-* - edit_item - Default is Edit Tag/Edit Category
+*/
-* - view_item - Default is View Tag/View Category
+function unregister_taxonomy( $taxonomy ) {
-* - update_item - Default is Update Tag/Update Category
+	if ( ! taxonomy_exists( $taxonomy ) ) {
-* - add_new_item - Default is Add New Tag/Add New Category
+		return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
-* - new_item_name - Default is New Tag Name/New Category Name
+	}
-* - separate_items_with_commas - This string isn't used on hierarchical taxonomies. Default is "Separate tags with commas", used in the meta box.
-* - add_or_remove_items - This string isn't used on hierarchical taxonomies. Default is "Add or remove tags", used in the meta box when JavaScript is disabled.
+	$taxonomy_object = get_taxonomy( $taxonomy );
-* - choose_from_most_used - This string isn't used on hierarchical taxonomies. Default is "Choose from the most used tags", used in the meta box.
-* - not_found - Default is "No tags found"/"No categories found", used in the meta box and taxonomy list table.
+	// Do not allow unregistering internal taxonomies.
-*
+	if ( $taxonomy_object->_builtin ) {
-* Above, the first default value is for non-hierarchical taxonomies (like tags) and the second one is for hierarchical taxonomies (like categories).
+		return new WP_Error( 'invalid_taxonomy', __( 'Unregistering a built-in taxonomy is not allowed.' ) );
+	}
+	global $wp_taxonomies;
+	$taxonomy_object->remove_rewrite_rules();
+	$taxonomy_object->remove_hooks();
+	// Remove the taxonomy.
+	unset( $wp_taxonomies[ $taxonomy ] );
+	/**
+	 * Fires after a taxonomy is unregistered.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param string $taxonomy Taxonomy name.
+	 */
+	do_action( 'unregistered_taxonomy', $taxonomy );
+	return true;
+}
+/**
+* Builds an object with all taxonomy labels out of a taxonomy object.
 *
 * @since 3.0.0
-* @param object $tax Taxonomy object
+* @since 4.3.0 Added the `no_terms` label.
-* @return object object with all the labels as member variables
+* @since 4.4.0 Added the `items_list_navigation` and `items_list` labels.
-*/
+* @since 4.9.0 Added the `most_used` and `back_to_items` labels.
+*
+* @param WP_Taxonomy $tax Taxonomy object.
+* @return object {
+*     Taxonomy labels object. The first default value is for non-hierarchical taxonomies
+*     (like tags) and the second one is for hierarchical taxonomies (like categories).
+*
+*     @type string $name                       General name for the taxonomy, usually plural. The same
+*                                              as and overridden by `$tax->label`. Default 'Tags'/'Categories'.
+*     @type string $singular_name              Name for one object of this taxonomy. Default 'Tag'/'Category'.
+*     @type string $search_items               Default 'Search Tags'/'Search Categories'.
+*     @type string $popular_items              This label is only used for non-hierarchical taxonomies.
+*                                              Default 'Popular Tags'.
+*     @type string $all_items                  Default 'All Tags'/'All Categories'.
+*     @type string $parent_item                This label is only used for hierarchical taxonomies. Default
+*                                              'Parent Category'.
+*     @type string $parent_item_colon          The same as `parent_item`, but with colon `:` in the end.
+*     @type string $edit_item                  Default 'Edit Tag'/'Edit Category'.
+*     @type string $view_item                  Default 'View Tag'/'View Category'.
+*     @type string $update_item                Default 'Update Tag'/'Update Category'.
+*     @type string $add_new_item               Default 'Add New Tag'/'Add New Category'.
+*     @type string $new_item_name              Default 'New Tag Name'/'New Category Name'.
+*     @type string $separate_items_with_commas This label is only used for non-hierarchical taxonomies. Default
+*                                              'Separate tags with commas', used in the meta box.
+*     @type string $add_or_remove_items        This label is only used for non-hierarchical taxonomies. Default
+*                                              'Add or remove tags', used in the meta box when JavaScript
+*                                              is disabled.
+*     @type string $choose_from_most_used      This label is only used on non-hierarchical taxonomies. Default
+*                                              'Choose from the most used tags', used in the meta box.
+*     @type string $not_found                  Default 'No tags found'/'No categories found', used in
+*                                              the meta box and taxonomy list table.
+*     @type string $no_terms                   Default 'No tags'/'No categories', used in the posts and media
+*                                              list tables.
+*     @type string $items_list_navigation      Label for the table pagination hidden heading.
+*     @type string $items_list                 Label for the table hidden heading.
+*     @type string $most_used                  Title for the Most Used tab. Default 'Most Used'.
+*     @type string $back_to_items              Label displayed after a term has been updated.
+* }
+*/
 function get_taxonomy_labels( $tax ) {
 	$tax->labels = (array) $tax->labels;
 	if ( isset( $tax->helps ) && empty( $tax->labels['separate_items_with_commas'] ) )
 		$tax->labels['separate_items_with_commas'] = $tax->helps;
 		'new_item_name' => array( __( 'New Tag Name' ), __( 'New Category Name' ) ),
 		'separate_items_with_commas' => array( __( 'Separate tags with commas' ), null ),
 		'add_or_remove_items' => array( __( 'Add or remove tags' ), null ),
 		'choose_from_most_used' => array( __( 'Choose from the most used tags' ), null ),
 		'not_found' => array( __( 'No tags found.' ), __( 'No categories found.' ) ),
+		'no_terms' => array( __( 'No tags' ), __( 'No categories' ) ),
+		'items_list_navigation' => array( __( 'Tags list navigation' ), __( 'Categories list navigation' ) ),
+		'items_list' => array( __( 'Tags list' ), __( 'Categories list' ) ),
+		/* translators: Tab heading when selecting from the most used terms */
+		'most_used' => array( _x( 'Most Used', 'tags' ), _x( 'Most Used', 'categories' ) ),
+		'back_to_items' => array( __( '&larr; Back to Tags' ), __( '&larr; Back to Categories' ) ),
 	);
 	$nohier_vs_hier_defaults['menu_name'] = $nohier_vs_hier_defaults['name'];
-	return _get_custom_object_labels( $tax, $nohier_vs_hier_defaults );
+	$labels = _get_custom_object_labels( $tax, $nohier_vs_hier_defaults );
+	$taxonomy = $tax->name;
+	$default_labels = clone $labels;
+	/**
+	 * Filters the labels of a specific taxonomy.
+	 *
+	 * The dynamic portion of the hook name, `$taxonomy`, refers to the taxonomy slug.
+	 *
+	 * @since 4.4.0
+	 *
+	 * @see get_taxonomy_labels() for the full list of taxonomy labels.
+	 *
+	 * @param object $labels Object with labels for the taxonomy as member variables.
+	 */
+	$labels = apply_filters( "taxonomy_labels_{$taxonomy}", $labels );
+	// Ensure that the filtered labels contain all required default values.
+	$labels = (object) array_merge( (array) $default_labels, (array) $labels );
+	return $labels;
 }
 /**
 * Add an already registered taxonomy to an object type.
 *
 * @since 3.0.0
-* @uses $wp_taxonomies Modifies taxonomy object
+*
-*
+* @global array $wp_taxonomies The registered taxonomies.
-* @param string $taxonomy Name of taxonomy object
+*
-* @param string $object_type Name of the object type
+* @param string $taxonomy    Name of taxonomy object.
-* @return bool True if successful, false if not
+* @param string $object_type Name of the object type.
+* @return bool True if successful, false if not.
 */
 function register_taxonomy_for_object_type( $taxonomy, $object_type) {
 	global $wp_taxonomies;
 	if ( !isset($wp_taxonomies[$taxonomy]) )
 		return false;
 	if ( ! in_array( $object_type, $wp_taxonomies[$taxonomy]->object_type ) )
 		$wp_taxonomies[$taxonomy]->object_type[] = $object_type;
+	// Filter out empties.
+	$wp_taxonomies[ $taxonomy ]->object_type = array_filter( $wp_taxonomies[ $taxonomy ]->object_type );
 	return true;
 }
 /**
 * Remove an already registered taxonomy from an object type.
 *
 * @since 3.7.0
+*
+* @global array $wp_taxonomies The registered taxonomies.
 *
 * @param string $taxonomy    Name of taxonomy object.
 * @param string $object_type Name of the object type.
 * @return bool True if successful, false if not.
 */
 *
 * @since 2.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
-* @param int|array $term_ids Term id or array of term ids of terms that will be used
+* @param int|array    $term_ids   Term id or array of term ids of terms that will be used.
-* @param string|array $taxonomies String of taxonomy name or Array of string values of taxonomy names
+* @param string|array $taxonomies String of taxonomy name or Array of string values of taxonomy names.
-* @param array|string $args Change the order of the object_ids, either ASC or DESC
+* @param array|string $args       Change the order of the object_ids, either ASC or DESC.
-* @return WP_Error|array If the taxonomy does not exist, then WP_Error will be returned. On success
+* @return WP_Error|array If the taxonomy does not exist, then WP_Error will be returned. On success.
 *	the array can be empty meaning that there are no $object_ids found or it will return the $object_ids found.
 */
 function get_objects_in_term( $term_ids, $taxonomies, $args = array() ) {
 	global $wpdb;
 	if ( ! is_array( $taxonomies ) ) {
 		$taxonomies = array( $taxonomies );
 	}
 	foreach ( (array) $taxonomies as $taxonomy ) {
 		if ( ! taxonomy_exists( $taxonomy ) ) {
-			return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy' ) );
+			return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
 		}
 	}
 	$defaults = array( 'order' => 'ASC' );
 	$args = wp_parse_args( $args, $defaults );
 	$order = ( 'desc' == strtolower( $args['order'] ) ) ? 'DESC' : 'ASC';
 	$term_ids = array_map('intval', $term_ids );
-	$taxonomies = "'" . implode( "', '", $taxonomies ) . "'";
+	$taxonomies = "'" . implode( "', '", array_map( 'esc_sql', $taxonomies ) ) . "'";
 	$term_ids = "'" . implode( "', '", $term_ids ) . "'";
-	$object_ids = $wpdb->get_col("SELECT tr.object_id FROM $wpdb->term_relationships AS tr INNER JOIN $wpdb->term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy IN ($taxonomies) AND tt.term_id IN ($term_ids) ORDER BY tr.object_id $order");
+	$sql = "SELECT tr.object_id FROM $wpdb->term_relationships AS tr INNER JOIN $wpdb->term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy IN ($taxonomies) AND tt.term_id IN ($term_ids) ORDER BY tr.object_id $order";
+	$last_changed = wp_cache_get_last_changed( 'terms' );
+	$cache_key = 'get_objects_in_term:' . md5( $sql ) . ":$last_changed";
+	$cache = wp_cache_get( $cache_key, 'terms' );
+	if ( false === $cache ) {
+		$object_ids = $wpdb->get_col( $sql );
+		wp_cache_set( $cache_key, $object_ids, 'terms' );
+	} else {
+		$object_ids = (array) $cache;
+	}
 	if ( ! $object_ids ){
 		return array();
 	}
 	return $object_ids;
 *
 * @since 3.1.0
 *
 * @see WP_Tax_Query
 *
-* @param array $tax_query A compact tax query
+* @param array  $tax_query         A compact tax query
 * @param string $primary_table
 * @param string $primary_id_column
 * @return array
 */
 function get_tax_sql( $tax_query, $primary_table, $primary_id_column ) {
 	$tax_query_obj = new WP_Tax_Query( $tax_query );
 	return $tax_query_obj->get_sql( $primary_table, $primary_id_column );
-}
-/**
-* Class for generating SQL clauses that filter a primary query according to object taxonomy terms.
-*
-* `WP_Tax_Query` is a helper that allows primary query classes, such as {@see WP_Query}, to filter
-* their results by object metadata, by generating `JOIN` and `WHERE` subclauses to be attached
-* to the primary SQL query string.
-*
-* @since 3.1.0
-*/
-class WP_Tax_Query {
-	/**
-	 * Array of taxonomy queries.
-	 *
-	 * See {@see WP_Tax_Query::__construct()} for information on tax query arguments.
-	 *
-	 * @since 3.1.0
-	 * @access public
-	 * @var array
-	 */
-	public $queries = array();
-	/**
-	 * The relation between the queries. Can be one of 'AND' or 'OR'.
-	 *
-	 * @since 3.1.0
-	 * @access public
-	 * @var string
-	 */
-	public $relation;
-	/**
-	 * Standard response when the query should not return any rows.
-	 *
-	 * @since 3.2.0
-	 * @access private
-	 * @var string
-	 */
-	private static $no_results = array( 'join' => array( '' ), 'where' => array( '0 = 1' ) );
-	/**
-	 * A flat list of table aliases used in the JOIN clauses.
-	 *
-	 * @since 4.1.0
-	 * @access protected
-	 * @var array
-	 */
-	protected $table_aliases = array();
-	/**
-	 * Terms and taxonomies fetched by this query.
-	 *
-	 * We store this data in a flat array because they are referenced in a
-	 * number of places by {@see WP_Query}.
-	 *
-	 * @since 4.1.0
-	 * @access public
-	 * @var array
-	 */
-	public $queried_terms = array();
-	/**
-	 * Database table that where the metadata's objects are stored (eg $wpdb->users).
-	 *
-	 * @since 4.1.0
-	 * @access public
-	 * @var string
-	 */
-	public $primary_table;
-	/**
-	 * Column in 'primary_table' that represents the ID of the object.
-	 *
-	 * @since 4.1.0
-	 * @access public
-	 * @var string
-	 */
-	public $primary_id_column;
-	/**
-	 * Constructor.
-	 *
-	 * @since 3.1.0
-	 * @since 4.1.0 Added support for `$operator` 'NOT EXISTS' and 'EXISTS' values.
-	 * @access public
-	 *
-	 * @param array $tax_query {
-	 *     Array of taxonomy query clauses.
-	 *
-	 *     @type string $relation Optional. The MySQL keyword used to join
-	 *                            the clauses of the query. Accepts 'AND', or 'OR'. Default 'AND'.
-	 *     @type array {
-	 *         Optional. An array of first-order clause parameters, or another fully-formed tax query.
-	 *
-	 *         @type string           $taxonomy         Taxonomy being queried. Optional when field=term_taxonomy_id.
-	 *         @type string|int|array $terms            Term or terms to filter by.
-	 *         @type string           $field            Field to match $terms against. Accepts 'term_id', 'slug',
-	 *                                                 'name', or 'term_taxonomy_id'. Default: 'term_id'.
-	 *         @type string           $operator         MySQL operator to be used with $terms in the WHERE clause.
-	 *                                                  Accepts 'AND', 'IN', 'NOT IN', 'EXISTS', 'NOT EXISTS'.
-	 *                                                  Default: 'IN'.
-	 *         @type bool             $include_children Optional. Whether to include child terms.
-	 *                                                  Requires a $taxonomy. Default: true.
-	 *     }
-	 * }
-	 */
-	public function __construct( $tax_query ) {
-		if ( isset( $tax_query['relation'] ) ) {
-			$this->relation = $this->sanitize_relation( $tax_query['relation'] );
-		} else {
-			$this->relation = 'AND';
-		}
-		$this->queries = $this->sanitize_query( $tax_query );
-	}
-	/**
-	 * Ensure the 'tax_query' argument passed to the class constructor is well-formed.
-	 *
-	 * Ensures that each query-level clause has a 'relation' key, and that
-	 * each first-order clause contains all the necessary keys from `$defaults`.
-	 *
-	 * @since 4.1.0
-	 * @access public
-	 *
-	 * @param array $queries Array of queries clauses.
-	 * @return array Sanitized array of query clauses.
-	 */
-	public function sanitize_query( $queries ) {
-		$cleaned_query = array();
-		$defaults = array(
-			'taxonomy' => '',
-			'terms' => array(),
-			'field' => 'term_id',
-			'operator' => 'IN',
-			'include_children' => true,
-		);
-		foreach ( $queries as $key => $query ) {
-			if ( 'relation' === $key ) {
-				$cleaned_query['relation'] = $this->sanitize_relation( $query );
-			// First-order clause.
-			} elseif ( self::is_first_order_clause( $query ) ) {
-				$cleaned_clause = array_merge( $defaults, $query );
-				$cleaned_clause['terms'] = (array) $cleaned_clause['terms'];
-				$cleaned_query[] = $cleaned_clause;
-				/*
-				 * Keep a copy of the clause in the flate
-				 * $queried_terms array, for use in WP_Query.
-				 */
-				if ( ! empty( $cleaned_clause['taxonomy'] ) && 'NOT IN' !== $cleaned_clause['operator'] ) {
-					$taxonomy = $cleaned_clause['taxonomy'];
-					if ( ! isset( $this->queried_terms[ $taxonomy ] ) ) {
-						$this->queried_terms[ $taxonomy ] = array();
-					}
-					/*
-					 * Backward compatibility: Only store the first
-					 * 'terms' and 'field' found for a given taxonomy.
-					 */
-					if ( ! empty( $cleaned_clause['terms'] ) && ! isset( $this->queried_terms[ $taxonomy ]['terms'] ) ) {
-						$this->queried_terms[ $taxonomy ]['terms'] = $cleaned_clause['terms'];
-					}
-					if ( ! empty( $cleaned_clause['field'] ) && ! isset( $this->queried_terms[ $taxonomy ]['field'] ) ) {
-						$this->queried_terms[ $taxonomy ]['field'] = $cleaned_clause['field'];
-					}
-				}
-			// Otherwise, it's a nested query, so we recurse.
-			} elseif ( is_array( $query ) ) {
-				$cleaned_subquery = $this->sanitize_query( $query );
-				if ( ! empty( $cleaned_subquery ) ) {
-					// All queries with children must have a relation.
-					if ( ! isset( $cleaned_subquery['relation'] ) ) {
-						$cleaned_subquery['relation'] = 'AND';
-					}
-					$cleaned_query[] = $cleaned_subquery;
-				}
-			}
-		}
-		return $cleaned_query;
-	}
-	/**
-	 * Sanitize a 'relation' operator.
-	 *
-	 * @since 4.1.0
-	 * @access public
-	 *
-	 * @param string $relation Raw relation key from the query argument.
-	 * @return string Sanitized relation ('AND' or 'OR').
-	 */
-	public function sanitize_relation( $relation ) {
-		if ( 'OR' === strtoupper( $relation ) ) {
-			return 'OR';
-		} else {
-			return 'AND';
-		}
-	}
-	/**
-	 * Determine whether a clause is first-order.
-	 *
-	 * A "first-order" clause is one that contains any of the first-order
-	 * clause keys ('terms', 'taxonomy', 'include_children', 'field',
-	 * 'operator'). An empty clause also counts as a first-order clause,
-	 * for backward compatibility. Any clause that doesn't meet this is
-	 * determined, by process of elimination, to be a higher-order query.
-	 *
-	 * @since 4.1.0
-	 * @access protected
-	 *
-	 * @param array $query Tax query arguments.
-	 * @return bool Whether the query clause is a first-order clause.
-	 */
-	protected static function is_first_order_clause( $query ) {
-		return is_array( $query ) && ( empty( $query ) || array_key_exists( 'terms', $query ) || array_key_exists( 'taxonomy', $query ) || array_key_exists( 'include_children', $query ) || array_key_exists( 'field', $query ) || array_key_exists( 'operator', $query ) );
-	}
-	/**
-	 * Generates SQL clauses to be appended to a main query.
-	 *
-	 * @since 3.1.0
-	 * @access public
-	 *
-	 * @param string $primary_table     Database table where the object being filtered is stored (eg wp_users).
-	 * @param string $primary_id_column ID column for the filtered object in $primary_table.
-	 * @return array {
-	 *     Array containing JOIN and WHERE SQL clauses to append to the main query.
-	 *
-	 *     @type string $join  SQL fragment to append to the main JOIN clause.
-	 *     @type string $where SQL fragment to append to the main WHERE clause.
-	 * }
-	 */
-	public function get_sql( $primary_table, $primary_id_column ) {
-		$this->primary_table = $primary_table;
-		$this->primary_id_column = $primary_id_column;
-		return $this->get_sql_clauses();
-	}
-	/**
-	 * Generate SQL clauses to be appended to a main query.
-	 *
-	 * Called by the public {@see WP_Tax_Query::get_sql()}, this method
-	 * is abstracted out to maintain parity with the other Query classes.
-	 *
-	 * @since 4.1.0
-	 * @access protected
-	 *
-	 * @return array {
-	 *     Array containing JOIN and WHERE SQL clauses to append to the main query.
-	 *
-	 *     @type string $join  SQL fragment to append to the main JOIN clause.
-	 *     @type string $where SQL fragment to append to the main WHERE clause.
-	 * }
-	 */
-	protected function get_sql_clauses() {
-		/*
-		 * $queries are passed by reference to get_sql_for_query() for recursion.
-		 * To keep $this->queries unaltered, pass a copy.
-		 */
-		$queries = $this->queries;
-		$sql = $this->get_sql_for_query( $queries );
-		if ( ! empty( $sql['where'] ) ) {
-			$sql['where'] = ' AND ' . $sql['where'];
-		}
-		return $sql;
-	}
-	/**
-	 * Generate SQL clauses for a single query array.
-	 *
-	 * If nested subqueries are found, this method recurses the tree to
-	 * produce the properly nested SQL.
-	 *
-	 * @since 4.1.0
-	 * @access protected
-	 *
-	 * @param array $query Query to parse, passed by reference.
-	 * @param int   $depth Optional. Number of tree levels deep we currently are.
-	 *                     Used to calculate indentation. Default 0.
-	 * @return array {
-	 *     Array containing JOIN and WHERE SQL clauses to append to a single query array.
-	 *
-	 *     @type string $join  SQL fragment to append to the main JOIN clause.
-	 *     @type string $where SQL fragment to append to the main WHERE clause.
-	 * }
-	 */
-	protected function get_sql_for_query( &$query, $depth = 0 ) {
-		$sql_chunks = array(
-			'join'  => array(),
-			'where' => array(),
-		);
-		$sql = array(
-			'join'  => '',
-			'where' => '',
-		);
-		$indent = '';
-		for ( $i = 0; $i < $depth; $i++ ) {
-			$indent .= "  ";
-		}
-		foreach ( $query as $key => &$clause ) {
-			if ( 'relation' === $key ) {
-				$relation = $query['relation'];
-			} elseif ( is_array( $clause ) ) {
-				// This is a first-order clause.
-				if ( $this->is_first_order_clause( $clause ) ) {
-					$clause_sql = $this->get_sql_for_clause( $clause, $query );
-					$where_count = count( $clause_sql['where'] );
-					if ( ! $where_count ) {
-						$sql_chunks['where'][] = '';
-					} elseif ( 1 === $where_count ) {
-						$sql_chunks['where'][] = $clause_sql['where'][0];
-					} else {
-						$sql_chunks['where'][] = '( ' . implode( ' AND ', $clause_sql['where'] ) . ' )';
-					}
-					$sql_chunks['join'] = array_merge( $sql_chunks['join'], $clause_sql['join'] );
-				// This is a subquery, so we recurse.
-				} else {
-					$clause_sql = $this->get_sql_for_query( $clause, $depth + 1 );
-					$sql_chunks['where'][] = $clause_sql['where'];
-					$sql_chunks['join'][]  = $clause_sql['join'];
-				}
-			}
-		}
-		// Filter to remove empties.
-		$sql_chunks['join']  = array_filter( $sql_chunks['join'] );
-		$sql_chunks['where'] = array_filter( $sql_chunks['where'] );
-		if ( empty( $relation ) ) {
-			$relation = 'AND';
-		}
-		// Filter duplicate JOIN clauses and combine into a single string.
-		if ( ! empty( $sql_chunks['join'] ) ) {
-			$sql['join'] = implode( ' ', array_unique( $sql_chunks['join'] ) );
-		}
-		// Generate a single WHERE clause with proper brackets and indentation.
-		if ( ! empty( $sql_chunks['where'] ) ) {
-			$sql['where'] = '( ' . "\n  " . $indent . implode( ' ' . "\n  " . $indent . $relation . ' ' . "\n  " . $indent, $sql_chunks['where'] ) . "\n" . $indent . ')';
-		}
-		return $sql;
-	}
-	/**
-	 * Generate SQL JOIN and WHERE clauses for a "first-order" query clause.
-	 *
-	 * @since 4.1.0
-	 * @access public
-	 *
-	 * @param array $clause       Query clause, passed by reference
-	 * @param array $parent_query Parent query array.
-	 * @return array {
-	 *     Array containing JOIN and WHERE SQL clauses to append to a first-order query.
-	 *
-	 *     @type string $join  SQL fragment to append to the main JOIN clause.
-	 *     @type string $where SQL fragment to append to the main WHERE clause.
-	 * }
-	 */
-	public function get_sql_for_clause( &$clause, $parent_query ) {
-		global $wpdb;
-		$sql = array(
-			'where' => array(),
-			'join'  => array(),
-		);
-		$join = '';
-		$this->clean_query( $clause );
-		if ( is_wp_error( $clause ) ) {
-			return self::$no_results;
-		}
-		$terms = $clause['terms'];
-		$operator = strtoupper( $clause['operator'] );
-		if ( 'IN' == $operator ) {
-			if ( empty( $terms ) ) {
-				return self::$no_results;
-			}
-			$terms = implode( ',', $terms );
-			/*
-			 * Before creating another table join, see if this clause has a
-			 * sibling with an existing join that can be shared.
-			 */
-			$alias = $this->find_compatible_table_alias( $clause, $parent_query );
-			if ( false === $alias ) {
-				$i = count( $this->table_aliases );
-				$alias = $i ? 'tt' . $i : $wpdb->term_relationships;
-				// Store the alias as part of a flat array to build future iterators.
-				$this->table_aliases[] = $alias;
-				// Store the alias with this clause, so later siblings can use it.
-				$clause['alias'] = $alias;
-				$join .= " INNER JOIN $wpdb->term_relationships";
-				$join .= $i ? " AS $alias" : '';
-				$join .= " ON ($this->primary_table.$this->primary_id_column = $alias.object_id)";
-			}
-			$where = "$alias.term_taxonomy_id $operator ($terms)";
-		} elseif ( 'NOT IN' == $operator ) {
-			if ( empty( $terms ) ) {
-				return $sql;
-			}
-			$terms = implode( ',', $terms );
-			$where = "$this->primary_table.$this->primary_id_column NOT IN (
-				SELECT object_id
-				FROM $wpdb->term_relationships
-				WHERE term_taxonomy_id IN ($terms)
-			)";
-		} elseif ( 'AND' == $operator ) {
-			if ( empty( $terms ) ) {
-				return $sql;
-			}
-			$num_terms = count( $terms );
-			$terms = implode( ',', $terms );
-			$where = "(
-				SELECT COUNT(1)
-				FROM $wpdb->term_relationships
-				WHERE term_taxonomy_id IN ($terms)
-				AND object_id = $this->primary_table.$this->primary_id_column
-			) = $num_terms";
-		} elseif ( 'NOT EXISTS' === $operator || 'EXISTS' === $operator ) {
-			$where = $wpdb->prepare( "$operator (
-				SELECT 1
-				FROM $wpdb->term_relationships
-				INNER JOIN $wpdb->term_taxonomy
-				ON $wpdb->term_taxonomy.term_taxonomy_id = $wpdb->term_relationships.term_taxonomy_id
-				WHERE $wpdb->term_taxonomy.taxonomy = %s
-				AND $wpdb->term_relationships.object_id = $this->primary_table.$this->primary_id_column
-			)", $clause['taxonomy'] );
-		}
-		$sql['join'][]  = $join;
-		$sql['where'][] = $where;
-		return $sql;
-	}
-	/**
-	 * Identify an existing table alias that is compatible with the current query clause.
-	 *
-	 * We avoid unnecessary table joins by allowing each clause to look for
-	 * an existing table alias that is compatible with the query that it
-	 * needs to perform.
-	 *
-	 * An existing alias is compatible if (a) it is a sibling of `$clause`
-	 * (ie, it's under the scope of the same relation), and (b) the combination
-	 * of operator and relation between the clauses allows for a shared table
-	 * join. In the case of {@see WP_Tax_Query}, this only applies to 'IN'
-	 * clauses that are connected by the relation 'OR'.
-	 *
-	 * @since 4.1.0
-	 * @access protected
-	 *
-	 * @param array       $clause       Query clause.
-	 * @param array       $parent_query Parent query of $clause.
-	 * @return string|bool Table alias if found, otherwise false.
-	 */
-	protected function find_compatible_table_alias( $clause, $parent_query ) {
-		$alias = false;
-		// Sanity check. Only IN queries use the JOIN syntax .
-		if ( ! isset( $clause['operator'] ) || 'IN' !== $clause['operator'] ) {
-			return $alias;
-		}
-		// Since we're only checking IN queries, we're only concerned with OR relations.
-		if ( ! isset( $parent_query['relation'] ) || 'OR' !== $parent_query['relation'] ) {
-			return $alias;
-		}
-		$compatible_operators = array( 'IN' );
-		foreach ( $parent_query as $sibling ) {
-			if ( ! is_array( $sibling ) || ! $this->is_first_order_clause( $sibling ) ) {
-				continue;
-			}
-			if ( empty( $sibling['alias'] ) || empty( $sibling['operator'] ) ) {
-				continue;
-			}
-			// The sibling must both have compatible operator to share its alias.
-			if ( in_array( strtoupper( $sibling['operator'] ), $compatible_operators ) ) {
-				$alias = $sibling['alias'];
-				break;
-			}
-		}
-		return $alias;
-	}
-	/**
-	 * Validates a single query.
-	 *
-	 * @since 3.2.0
-	 * @access private
-	 *
-	 * @param array &$query The single query.
-	 */
-	private function clean_query( &$query ) {
-		if ( empty( $query['taxonomy'] ) ) {
-			if ( 'term_taxonomy_id' !== $query['field'] ) {
-				$query = new WP_Error( 'Invalid taxonomy' );
-				return;
-			}
-			// so long as there are shared terms, include_children requires that a taxonomy is set
-			$query['include_children'] = false;
-		} elseif ( ! taxonomy_exists( $query['taxonomy'] ) ) {
-			$query = new WP_Error( 'Invalid taxonomy' );
-			return;
-		}
-		$query['terms'] = array_unique( (array) $query['terms'] );
-		if ( is_taxonomy_hierarchical( $query['taxonomy'] ) && $query['include_children'] ) {
-			$this->transform_query( $query, 'term_id' );
-			if ( is_wp_error( $query ) )
-				return;
-			$children = array();
-			foreach ( $query['terms'] as $term ) {
-				$children = array_merge( $children, get_term_children( $term, $query['taxonomy'] ) );
-				$children[] = $term;
-			}
-			$query['terms'] = $children;
-		}
-		$this->transform_query( $query, 'term_taxonomy_id' );
-	}
-	/**
-	 * Transforms a single query, from one field to another.
-	 *
-	 * @since 3.2.0
-	 *
-	 * @param array  &$query          The single query.
-	 * @param string $resulting_field The resulting field. Accepts 'slug', 'name', 'term_taxonomy_id',
-	 *                                or 'term_id'. Default: 'term_id'.
-	 */
-	public function transform_query( &$query, $resulting_field ) {
-		global $wpdb;
-		if ( empty( $query['terms'] ) )
-			return;
-		if ( $query['field'] == $resulting_field )
-			return;
-		$resulting_field = sanitize_key( $resulting_field );
-		switch ( $query['field'] ) {
-			case 'slug':
-			case 'name':
-				foreach ( $query['terms'] as &$term ) {
-					/*
-					 * 0 is the $term_id parameter. We don't have a term ID yet, but it doesn't
-					 * matter because `sanitize_term_field()` ignores the $term_id param when the
-					 * context is 'db'.
-					 */
-					$term = "'" . esc_sql( sanitize_term_field( $query['field'], $term, 0, $query['taxonomy'], 'db' ) ) . "'";
-				}
-				$terms = implode( ",", $query['terms'] );
-				$terms = $wpdb->get_col( "
-					SELECT $wpdb->term_taxonomy.$resulting_field
-					FROM $wpdb->term_taxonomy
-					INNER JOIN $wpdb->terms USING (term_id)
-					WHERE taxonomy = '{$query['taxonomy']}'
-					AND $wpdb->terms.{$query['field']} IN ($terms)
-				" );
-				break;
-			case 'term_taxonomy_id':
-				$terms = implode( ',', array_map( 'intval', $query['terms'] ) );
-				$terms = $wpdb->get_col( "
-					SELECT $resulting_field
-					FROM $wpdb->term_taxonomy
-					WHERE term_taxonomy_id IN ($terms)
-				" );
-				break;
-			default:
-				$terms = implode( ',', array_map( 'intval', $query['terms'] ) );
-				$terms = $wpdb->get_col( "
-					SELECT $resulting_field
-					FROM $wpdb->term_taxonomy
-					WHERE taxonomy = '{$query['taxonomy']}'
-					AND term_id IN ($terms)
-				" );
-		}
-		if ( 'AND' == $query['operator'] && count( $terms ) < count( $query['terms'] ) ) {
-			$query = new WP_Error( 'Inexistent terms' );
-			return;
-		}
-		$query['terms'] = $terms;
-		$query['field'] = $resulting_field;
-	}
 }
 /**
 * Get all Term data from database by Term ID.
 *
 * There are two hooks, one is specifically for each term, named 'get_term', and
 * the second is for the taxonomy name, 'term_$taxonomy'. Both hooks gets the
 * term object, and the taxonomy name as parameters. Both hooks are expected to
 * return a Term object.
 *
-* 'get_term' hook - Takes two parameters the term Object and the taxonomy name.
+* {@see 'get_term'} hook - Takes two parameters the term Object and the taxonomy name.
 * Must return term object. Used in get_term() as a catch-all filter for every
 * $term.
 *
-* 'get_$taxonomy' hook - Takes two parameters the term Object and the taxonomy
+* {@see 'get_$taxonomy'} hook - Takes two parameters the term Object and the taxonomy
 * name. Must return term object. $taxonomy will be the taxonomy name, so for
 * example, if 'category', it would be 'get_category' as the filter name. Useful
 * for custom taxonomies or plugging into default taxonomies.
 *
+* @todo Better formatting for DocBlock
+*
 * @since 2.3.0
-*
+* @since 4.4.0 Converted to return a WP_Term object if `$output` is `OBJECT`.
-* @global wpdb $wpdb WordPress database abstraction object.
+*              The `$taxonomy` parameter was made optional.
+*
 * @see sanitize_term_field() The $context param lists the available values for get_term_by() $filter param.
 *
-* @param int|object $term If integer, will get from database. If object will apply filters and return $term.
+* @param int|WP_Term|object $term If integer, term data will be fetched from the database, or from the cache if
-* @param string $taxonomy Taxonomy name that $term is part of.
+*                                 available. If stdClass object (as in the results of a database query), will apply
-* @param string $output Constant OBJECT, ARRAY_A, or ARRAY_N
+*                                 filters and return a `WP_Term` object corresponding to the `$term` data. If `WP_Term`,
-* @param string $filter Optional, default is raw or no WordPress defined filter will applied.
+*                                 will return `$term`.
-* @return mixed|null|WP_Error Term Row from database. Will return null if $term is empty. If taxonomy does not
+* @param string     $taxonomy Optional. Taxonomy name that $term is part of.
-* exist then WP_Error will be returned.
+* @param string     $output   Optional. The required return type. One of OBJECT, ARRAY_A, or ARRAY_N, which correspond to
-*/
+*                             a WP_Term object, an associative array, or a numeric array, respectively. Default OBJECT.
-function get_term($term, $taxonomy, $output = OBJECT, $filter = 'raw') {
+* @param string     $filter   Optional, default is raw or no WordPress defined filter will applied.
-	global $wpdb;
+* @return array|WP_Term|WP_Error|null Object of the type specified by `$output` on success. When `$output` is 'OBJECT',
+*                                     a WP_Term instance is returned. If taxonomy does not exist, a WP_Error is
-	if ( empty($term) ) {
+*                                     returned. Returns null for miscellaneous failure.
-		$error = new WP_Error('invalid_term', __('Empty Term'));
+*/
-		return $error;
+function get_term( $term, $taxonomy = '', $output = OBJECT, $filter = 'raw' ) {
-	}
+	if ( empty( $term ) ) {
+		return new WP_Error( 'invalid_term', __( 'Empty Term.' ) );
-	if ( ! taxonomy_exists($taxonomy) ) {
+	}
-		$error = new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));
-		return $error;
+	if ( $taxonomy && ! taxonomy_exists( $taxonomy ) ) {
-	}
+		return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
+	}
-	if ( is_object($term) && empty($term->filter) ) {
-		wp_cache_add( $term->term_id, $term, $taxonomy );
+	if ( $term instanceof WP_Term ) {
 		$_term = $term;
+	} elseif ( is_object( $term ) ) {
+		if ( empty( $term->filter ) || 'raw' === $term->filter ) {
+			$_term = sanitize_term( $term, $taxonomy, 'raw' );
+			$_term = new WP_Term( $_term );
+		} else {
+			$_term = WP_Term::get_instance( $term->term_id );
+		}
 	} else {
-		if ( is_object($term) )
+		$_term = WP_Term::get_instance( $term, $taxonomy );
-			$term = $term->term_id;
+	}
-		if ( !$term = (int) $term )
-			return null;
+	if ( is_wp_error( $_term ) ) {
-		if ( ! $_term = wp_cache_get( $term, $taxonomy ) ) {
+		return $_term;
-			$_term = $wpdb->get_row( $wpdb->prepare( "SELECT t.*, tt.* FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy = %s AND t.term_id = %d LIMIT 1", $taxonomy, $term) );
+	} elseif ( ! $_term ) {
-			if ( ! $_term )
+		return null;
-				return null;
-			wp_cache_add( $term, $_term, $taxonomy );
-		}
 	}
 	/**
-	 * Filter a term.
+	 * Filters a term.
 	 *
 	 * @since 2.3.0
-	 *
+	 * @since 4.4.0 `$_term` can now also be a WP_Term object.
-	 * @param int|object $_term    Term object or ID.
+	 *
-	 * @param string     $taxonomy The taxonomy slug.
+	 * @param int|WP_Term $_term    Term object or ID.
+	 * @param string      $taxonomy The taxonomy slug.
 	 */
 	$_term = apply_filters( 'get_term', $_term, $taxonomy );
 	/**
-	 * Filter a taxonomy.
+	 * Filters a taxonomy.
 	 *
 	 * The dynamic portion of the filter name, `$taxonomy`, refers
 	 * to the taxonomy slug.
 	 *
 	 * @since 2.3.0
-	 *
+	 * @since 4.4.0 `$_term` can now also be a WP_Term object.
-	 * @param int|object $_term    Term object or ID.
+	 *
-	 * @param string     $taxonomy The taxonomy slug.
+	 * @param int|WP_Term $_term    Term object or ID.
-	 */
+	 * @param string      $taxonomy The taxonomy slug.
-	$_term = apply_filters( "get_$taxonomy", $_term, $taxonomy );
+	 */
-	$_term = sanitize_term($_term, $taxonomy, $filter);
+	$_term = apply_filters( "get_{$taxonomy}", $_term, $taxonomy );
-	if ( $output == OBJECT ) {
+	// Bail if a filter callback has changed the type of the `$_term` object.
+	if ( ! ( $_term instanceof WP_Term ) ) {
 		return $_term;
-	} elseif ( $output == ARRAY_A ) {
+	}
-		$__term = get_object_vars($_term);
-		return $__term;
+	// Sanitize term, according to the specified filter.
+	$_term->filter( $filter );
+	if ( $output == ARRAY_A ) {
+		return $_term->to_array();
 	} elseif ( $output == ARRAY_N ) {
-		$__term = array_values(get_object_vars($_term));
+		return array_values( $_term->to_array() );
-		return $__term;
+	}
-	} else {
-		return $_term;
+	return $_term;
-	}
 }
 /**
 * Get all Term data from database by Term field and data.
 *
 * field, but not recommended that you do so.
 *
 * If $value does not exist, the return value will be false. If $taxonomy exists
 * and $field and $value combinations exist, the Term will be returned.
 *
+* This function will always return the first term that matches the `$field`-
+* `$value`-`$taxonomy` combination specified in the parameters. If your query
+* is likely to match more than one term (as is likely to be the case when
+* `$field` is 'name', for example), consider using get_terms() instead; that
+* way, you will get all matching terms, and can provide your own logic for
+* deciding which one was intended.
+*
+* @todo Better formatting for DocBlock.
+*
 * @since 2.3.0
-*
+* @since 4.4.0 `$taxonomy` is optional if `$field` is 'term_taxonomy_id'. Converted to return
-* @global wpdb $wpdb WordPress database abstraction object.
+*              a WP_Term object if `$output` is `OBJECT`.
+*
 * @see sanitize_term_field() The $context param lists the available values for get_term_by() $filter param.
 *
-* @param string $field Either 'slug', 'name', 'id' (term_id), or 'term_taxonomy_id'
+* @param string     $field    Either 'slug', 'name', 'id' (term_id), or 'term_taxonomy_id'
-* @param string|int $value Search for this term value
+* @param string|int $value    Search for this term value
-* @param string $taxonomy Taxonomy Name
+* @param string     $taxonomy Taxonomy name. Optional, if `$field` is 'term_taxonomy_id'.
-* @param string $output Constant OBJECT, ARRAY_A, or ARRAY_N
+* @param string     $output   Optional. The required return type. One of OBJECT, ARRAY_A, or ARRAY_N, which correspond to
-* @param string $filter Optional, default is raw or no WordPress defined filter will applied.
+*                             a WP_Term object, an associative array, or a numeric array, respectively. Default OBJECT.
-* @return mixed Term Row from database. Will return false if $taxonomy does not exist or $term was not found.
+* @param string     $filter   Optional, default is raw or no WordPress defined filter will applied.
-*/
+* @return WP_Term|array|false WP_Term instance (or array) on success. Will return false if `$taxonomy` does not exist
-function get_term_by($field, $value, $taxonomy, $output = OBJECT, $filter = 'raw') {
+*                             or `$term` was not found.
-	global $wpdb;
+*/
+function get_term_by( $field, $value, $taxonomy = '', $output = OBJECT, $filter = 'raw' ) {
-	if ( ! taxonomy_exists($taxonomy) )
+	// 'term_taxonomy_id' lookups don't require taxonomy checks.
+	if ( 'term_taxonomy_id' !== $field && ! taxonomy_exists( $taxonomy ) ) {
 		return false;
+	}
-	if ( 'slug' == $field ) {
-		$field = 't.slug';
+	// No need to perform a query for empty 'slug' or 'name'.
-		$value = sanitize_title($value);
+	if ( 'slug' === $field || 'name' === $field ) {
-		if ( empty($value) )
+		$value = (string) $value;
+		if ( 0 === strlen( $value ) ) {
 			return false;
-	} elseif ( 'name' == $field ) {
+		}
-		// Assume already escaped
+	}
-		$value = wp_unslash($value);
-		$field = 't.name';
+	if ( 'id' === $field || 'term_id' === $field ) {
-	} elseif ( 'term_taxonomy_id' == $field ) {
-		$value = (int) $value;
-		$field = 'tt.term_taxonomy_id';
-	} else {
 		$term = get_term( (int) $value, $taxonomy, $output, $filter );
-		if ( is_wp_error( $term ) )
+		if ( is_wp_error( $term ) || null === $term ) {
 			$term = false;
+		}
 		return $term;
 	}
-	$term = $wpdb->get_row( $wpdb->prepare( "SELECT t.*, tt.* FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy = %s AND $field = %s LIMIT 1", $taxonomy, $value ) );
+	$args = array(
-	if ( ! $term )
+		'get'                    => 'all',
+		'number'                 => 1,
+		'taxonomy'               => $taxonomy,
+		'update_term_meta_cache' => false,
+		'orderby'                => 'none',
+		'suppress_filter'        => true,
+	);
+	switch ( $field ) {
+		case 'slug' :
+			$args['slug'] = $value;
+			break;
+		case 'name' :
+			$args['name'] = $value;
+			break;
+		case 'term_taxonomy_id' :
+			$args['term_taxonomy_id'] = $value;
+			unset( $args[ 'taxonomy' ] );
+			break;
+		default :
+			return false;
+	}
+	$terms = get_terms( $args );
+	if ( is_wp_error( $terms ) || empty( $terms ) ) {
 		return false;
+	}
-	wp_cache_add( $term->term_id, $term, $taxonomy );
+	$term = array_shift( $terms );
-	/** This filter is documented in wp-includes/taxonomy.php */
-	$term = apply_filters( 'get_term', $term, $taxonomy );
+	// In the case of 'term_taxonomy_id', override the provided `$taxonomy` with whatever we find in the db.
+	if ( 'term_taxonomy_id' === $field ) {
-	/** This filter is documented in wp-includes/taxonomy.php */
+		$taxonomy = $term->taxonomy;
-	$term = apply_filters( "get_$taxonomy", $term, $taxonomy );
+	}
-	$term = sanitize_term($term, $taxonomy, $filter);
+	return get_term( $term, $taxonomy, $output, $filter );
-	if ( $output == OBJECT ) {
-		return $term;
-	} elseif ( $output == ARRAY_A ) {
-		return get_object_vars($term);
-	} elseif ( $output == ARRAY_N ) {
-		return array_values(get_object_vars($term));
-	} else {
-		return $term;
-	}
 }
 /**
 * Merge all term children into a single array of their IDs.
 *
 *
 * Will return an empty array if $term does not exist in $taxonomy.
 *
 * @since 2.3.0
 *
-* @global wpdb $wpdb WordPress database abstraction object.
+* @param int    $term_id  ID of Term to get children.
-*
+* @param string $taxonomy Taxonomy Name.
-* @param string $term_id ID of Term to get children
+* @return array|WP_Error List of Term IDs. WP_Error returned if `$taxonomy` does not exist.
-* @param string $taxonomy Taxonomy Name
-* @return array|WP_Error List of Term IDs. WP_Error returned if $taxonomy does not exist
 */
 function get_term_children( $term_id, $taxonomy ) {
-	if ( ! taxonomy_exists($taxonomy) )
+	if ( ! taxonomy_exists( $taxonomy ) ) {
-		return new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));
+		return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
+	}
 	$term_id = intval( $term_id );
 	$terms = _get_term_hierarchy($taxonomy);
 }
 /**
 * Get sanitized Term field.
 *
-* Does checks for $term, based on the $taxonomy. The function is for contextual
+* The function is for contextual reasons and for simplicity of usage.
-* reasons and for simplicity of usage. See sanitize_term_field() for more
-* information.
 *
 * @since 2.3.0
-*
+* @since 4.4.0 The `$taxonomy` parameter was made optional. `$term` can also now accept a WP_Term object.
-* @param string $field Term field to fetch
+*
-* @param int $term Term ID
+* @see sanitize_term_field()
-* @param string $taxonomy Taxonomy Name
+*
-* @param string $context Optional, default is display. Look at sanitize_term_field() for available options.
+* @param string      $field    Term field to fetch.
-* @return mixed Will return an empty string if $term is not an object or if $field is not set in $term.
+* @param int|WP_Term $term     Term ID or object.
-*/
+* @param string      $taxonomy Optional. Taxonomy Name. Default empty.
-function get_term_field( $field, $term, $taxonomy, $context = 'display' ) {
+* @param string      $context  Optional, default is display. Look at sanitize_term_field() for available options.
-	$term = (int) $term;
+* @return string|int|null|WP_Error Will return an empty string if $term is not an object or if $field is not set in $term.
+*/
+function get_term_field( $field, $term, $taxonomy = '', $context = 'display' ) {
 	$term = get_term( $term, $taxonomy );
 	if ( is_wp_error($term) )
 		return $term;
 	if ( !is_object($term) )
 		return '';
 	if ( !isset($term->$field) )
 		return '';
-	return sanitize_term_field($field, $term->$field, $term->term_id, $taxonomy, $context);
+	return sanitize_term_field( $field, $term->$field, $term->term_id, $term->taxonomy, $context );
 }
 /**
 * Sanitizes Term for editing.
 *
 * Return value is sanitize_term() and usage is for sanitizing the term for
 * editing. Function is for contextual and simplicity.
 *
 * @since 2.3.0
 *
-* @param int|object $id Term ID or Object
+* @param int|object $id       Term ID or object.
-* @param string $taxonomy Taxonomy Name
+* @param string     $taxonomy Taxonomy name.
-* @return mixed|null|WP_Error Will return empty string if $term is not an object.
+* @return string|int|null|WP_Error Will return empty string if $term is not an object.
 */
 function get_term_to_edit( $id, $taxonomy ) {
 	$term = get_term( $id, $taxonomy );
 	if ( is_wp_error($term) )
 * Retrieve the terms in a given taxonomy or list of taxonomies.
 *
 * You can fully inject any customizations to the query before it is sent, as
 * well as control the output with a filter.
 *
-* The 'get_terms' filter will be called when the cache has the term and will
+* The {@see 'get_terms'} filter will be called when the cache has the term and will
 * pass the found term along with the array of $taxonomies and array of $args.
 * This filter is also called before the array of terms is passed and will pass
 * the array of terms, along with the $taxonomies and $args.
 *
-* The 'list_terms_exclusions' filter passes the compiled exclusions along with
+* The {@see 'list_terms_exclusions'} filter passes the compiled exclusions along with
 * the $args.
 *
-* The 'get_terms_orderby' filter passes the ORDER BY clause for the query
+* The {@see 'get_terms_orderby'} filter passes the `ORDER BY` clause for the query
 * along with the $args array.
+*
+* Prior to 4.5.0, the first parameter of `get_terms()` was a taxonomy or list of taxonomies:
+*
+*     $terms = get_terms( 'post_tag', array(
+*         'hide_empty' => false,
+*     ) );
+*
+* Since 4.5.0, taxonomies should be passed via the 'taxonomy' argument in the `$args` array:
+*
+*     $terms = get_terms( array(
+*         'taxonomy' => 'post_tag',
+*         'hide_empty' => false,
+*     ) );
 *
 * @since 2.3.0
 * @since 4.2.0 Introduced 'name' and 'childless' parameters.
+* @since 4.4.0 Introduced the ability to pass 'term_id' as an alias of 'id' for the `orderby` parameter.
+*              Introduced the 'meta_query' and 'update_term_meta_cache' parameters. Converted to return
+*              a list of WP_Term objects.
+* @since 4.5.0 Changed the function signature so that the `$args` array can be provided as the first parameter.
+*              Introduced 'meta_key' and 'meta_value' parameters. Introduced the ability to order results by metadata.
+* @since 4.8.0 Introduced 'suppress_filter' parameter.
+*
+* @internal The `$deprecated` parameter is parsed for backward compatibility only.
+*
+* @param string|array $args       Optional. Array or string of arguments. See WP_Term_Query::__construct()
+*                                 for information on accepted arguments. Default empty.
+* @param array        $deprecated Argument array, when using the legacy function parameter format. If present, this
+*                                 parameter will be interpreted as `$args`, and the first function parameter will
+*                                 be parsed as a taxonomy or array of taxonomies.
+* @return array|int|WP_Error List of WP_Term instances and their children. Will return WP_Error, if any of $taxonomies
+*                            do not exist.
+*/
+function get_terms( $args = array(), $deprecated = '' ) {
+	$term_query = new WP_Term_Query();
+	$defaults = array(
+		'suppress_filter' => false,
+	);
+	/*
+	 * Legacy argument format ($taxonomy, $args) takes precedence.
+	 *
+	 * We detect legacy argument format by checking if
+	 * (a) a second non-empty parameter is passed, or
+	 * (b) the first parameter shares no keys with the default array (ie, it's a list of taxonomies)
+	 */
+	$_args = wp_parse_args( $args );
+	$key_intersect  = array_intersect_key( $term_query->query_var_defaults, (array) $_args );
+	$do_legacy_args = $deprecated || empty( $key_intersect );
+	if ( $do_legacy_args ) {
+		$taxonomies = (array) $args;
+		$args = wp_parse_args( $deprecated, $defaults );
+		$args['taxonomy'] = $taxonomies;
+	} else {
+		$args = wp_parse_args( $args, $defaults );
+		if ( isset( $args['taxonomy'] ) && null !== $args['taxonomy'] ) {
+			$args['taxonomy'] = (array) $args['taxonomy'];
+		}
+	}
+	if ( ! empty( $args['taxonomy'] ) ) {
+		foreach ( $args['taxonomy'] as $taxonomy ) {
+			if ( ! taxonomy_exists( $taxonomy ) ) {
+				return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
+			}
+		}
+	}
+	// Don't pass suppress_filter to WP_Term_Query.
+	$suppress_filter = $args['suppress_filter'];
+	unset( $args['suppress_filter'] );
+	$terms = $term_query->query( $args );
+	// Count queries are not filtered, for legacy reasons.
+	if ( ! is_array( $terms ) ) {
+		return $terms;
+	}
+	if ( $suppress_filter ) {
+		return $terms;
+	}
+	/**
+	 * Filters the found terms.
+	 *
+	 * @since 2.3.0
+	 * @since 4.6.0 Added the `$term_query` parameter.
+	 *
+	 * @param array         $terms      Array of found terms.
+	 * @param array         $taxonomies An array of taxonomies.
+	 * @param array         $args       An array of get_terms() arguments.
+	 * @param WP_Term_Query $term_query The WP_Term_Query object.
+	 */
+	return apply_filters( 'get_terms', $terms, $term_query->query_vars['taxonomy'], $term_query->query_vars, $term_query );
+}
+/**
+* Adds metadata to a term.
+*
+* @since 4.4.0
+*
+* @param int    $term_id    Term ID.
+* @param string $meta_key   Metadata name.
+* @param mixed  $meta_value Metadata value.
+* @param bool   $unique     Optional. Whether to bail if an entry with the same key is found for the term.
+*                           Default false.
+* @return int|WP_Error|bool Meta ID on success. WP_Error when term_id is ambiguous between taxonomies.
+*                           False on failure.
+*/
+function add_term_meta( $term_id, $meta_key, $meta_value, $unique = false ) {
+	// Bail if term meta table is not installed.
+	if ( get_option( 'db_version' ) < 34370 ) {
+		return false;
+	}
+	if ( wp_term_is_shared( $term_id ) ) {
+		return new WP_Error( 'ambiguous_term_id', __( 'Term meta cannot be added to terms that are shared between taxonomies.'), $term_id );
+	}
+	$added = add_metadata( 'term', $term_id, $meta_key, $meta_value, $unique );
+	// Bust term query cache.
+	if ( $added ) {
+		wp_cache_set( 'last_changed', microtime(), 'terms' );
+	}
+	return $added;
+}
+/**
+* Removes metadata matching criteria from a term.
+*
+* @since 4.4.0
+*
+* @param int    $term_id    Term ID.
+* @param string $meta_key   Metadata name.
+* @param mixed  $meta_value Optional. Metadata value. If provided, rows will only be removed that match the value.
+* @return bool True on success, false on failure.
+*/
+function delete_term_meta( $term_id, $meta_key, $meta_value = '' ) {
+	// Bail if term meta table is not installed.
+	if ( get_option( 'db_version' ) < 34370 ) {
+		return false;
+	}
+	$deleted = delete_metadata( 'term', $term_id, $meta_key, $meta_value );
+	// Bust term query cache.
+	if ( $deleted ) {
+		wp_cache_set( 'last_changed', microtime(), 'terms' );
+	}
+	return $deleted;
+}
+/**
+* Retrieves metadata for a term.
+*
+* @since 4.4.0
+*
+* @param int    $term_id Term ID.
+* @param string $key     Optional. The meta key to retrieve. If no key is provided, fetches all metadata for the term.
+* @param bool   $single  Whether to return a single value. If false, an array of all values matching the
+*                        `$term_id`/`$key` pair will be returned. Default: false.
+* @return mixed If `$single` is false, an array of metadata values. If `$single` is true, a single metadata value.
+*/
+function get_term_meta( $term_id, $key = '', $single = false ) {
+	// Bail if term meta table is not installed.
+	if ( get_option( 'db_version' ) < 34370 ) {
+		return false;
+	}
+	return get_metadata( 'term', $term_id, $key, $single );
+}
+/**
+* Updates term metadata.
+*
+* Use the `$prev_value` parameter to differentiate between meta fields with the same key and term ID.
+*
+* If the meta field for the term does not exist, it will be added.
+*
+* @since 4.4.0
+*
+* @param int    $term_id    Term ID.
+* @param string $meta_key   Metadata key.
+* @param mixed  $meta_value Metadata value.
+* @param mixed  $prev_value Optional. Previous value to check before removing.
+* @return int|WP_Error|bool Meta ID if the key didn't previously exist. True on successful update.
+*                           WP_Error when term_id is ambiguous between taxonomies. False on failure.
+*/
+function update_term_meta( $term_id, $meta_key, $meta_value, $prev_value = '' ) {
+	// Bail if term meta table is not installed.
+	if ( get_option( 'db_version' ) < 34370 ) {
+		return false;
+	}
+	if ( wp_term_is_shared( $term_id ) ) {
+		return new WP_Error( 'ambiguous_term_id', __( 'Term meta cannot be added to terms that are shared between taxonomies.'), $term_id );
+	}
+	$updated = update_metadata( 'term', $term_id, $meta_key, $meta_value, $prev_value );
+	// Bust term query cache.
+	if ( $updated ) {
+		wp_cache_set( 'last_changed', microtime(), 'terms' );
+	}
+	return $updated;
+}
+/**
+* Updates metadata cache for list of term IDs.
+*
+* Performs SQL query to retrieve all metadata for the terms matching `$term_ids` and stores them in the cache.
+* Subsequent calls to `get_term_meta()` will not need to query the database.
+*
+* @since 4.4.0
+*
+* @param array $term_ids List of term IDs.
+* @return array|false Returns false if there is nothing to update. Returns an array of metadata on success.
+*/
+function update_termmeta_cache( $term_ids ) {
+	// Bail if term meta table is not installed.
+	if ( get_option( 'db_version' ) < 34370 ) {
+		return;
+	}
+	return update_meta_cache( 'term', $term_ids );
+}
+/**
+* Get all meta data, including meta IDs, for the given term ID.
+*
+* @since 4.9.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
-* @param string|array $taxonomies Taxonomy name or list of Taxonomy names.
+* @param int $term_id Term ID.
-* @param array|string $args {
+* @return array|false Array with meta data, or false when the meta table is not installed.
-*     Optional. Array or string of arguments to get terms.
+*/
-*
+function has_term_meta( $term_id ) {
-*     @type string       $orderby           Field(s) to order terms by. Accepts term fields ('name', 'slug',
+	// Bail if term meta table is not installed.
-*                                           'term_group', 'term_id', 'id', 'description'), 'count' for term
+	if ( get_option( 'db_version' ) < 34370 ) {
-*                                           taxonomy count, 'include' to match the 'order' of the $include param,
+		return false;
-*                                           or 'none' to skip ORDER BY. Defaults to 'name'.
+	}
-*     @type string       $order             Whether to order terms in ascending or descending order.
-*                                           Accepts 'ASC' (ascending) or 'DESC' (descending).
-*                                           Default 'ASC'.
-*     @type bool|int     $hide_empty        Whether to hide terms not assigned to any posts. Accepts
-*                                           1|true or 0|false. Default 1|true.
-*     @type array|string $include           Array or comma/space-separated string of term ids to include.
-*                                           Default empty array.
-*     @type array|string $exclude           Array or comma/space-separated string of term ids to exclude.
-*                                           If $include is non-empty, $exclude is ignored.
-*                                           Default empty array.
-*     @type array|string $exclude_tree      Array or comma/space-separated string of term ids to exclude
-*                                           along with all of their descendant terms. If $include is
-*                                           non-empty, $exclude_tree is ignored. Default empty array.
-*     @type int|string   $number            Maximum number of terms to return. Accepts ''|0 (all) or any
-*                                           positive number. Default ''|0 (all).
-*     @type int          $offset            The number by which to offset the terms query. Default empty.
-*     @type string       $fields            Term fields to query for. Accepts 'all' (returns an array of
-*                                           term objects), 'ids' or 'names' (returns an array of integers
-*                                           or strings, respectively. Default 'all'.
-*     @type string|array $name              Optional. Name or array of names to return term(s) for. Default empty.
-*     @type string|array $slug              Optional. Slug or array of slugs to return term(s) for. Default empty.
-*     @type bool         $hierarchical      Whether to include terms that have non-empty descendants (even
-*                                           if $hide_empty is set to true). Default true.
-*     @type string       $search            Search criteria to match terms. Will be SQL-formatted with
-*                                           wildcards before and after. Default empty.
-*     @type string       $name__like        Retrieve terms with criteria by which a term is LIKE $name__like.
-*                                           Default empty.
-*     @type string       $description__like Retrieve terms where the description is LIKE $description__like.
-*                                           Default empty.
-*     @type bool         $pad_counts        Whether to pad the quantity of a term's children in the quantity
-*                                           of each term's "count" object variable. Default false.
-*     @type string       $get               Whether to return terms regardless of ancestry or whether the terms
-*                                           are empty. Accepts 'all' or empty (disabled). Default empty.
-*     @type int          $child_of          Term ID to retrieve child terms of. If multiple taxonomies
-*                                           are passed, $child_of is ignored. Default 0.
-*     @type int|string   $parent            Parent term ID to retrieve direct-child terms of. Default empty.
-*     @type bool         $childless         True to limit results to terms that have no children. This parameter has
-*                                           no effect on non-hierarchical taxonomies. Default false.
-*     @type string       $cache_domain      Unique cache key to be produced when this query is stored in an
-*                                           object cache. Default is 'core'.
-* }
-* @return array|WP_Error List of Term Objects and their children. Will return WP_Error, if any of $taxonomies
-*                        do not exist.
-*/
-function get_terms( $taxonomies, $args = '' ) {
 	global $wpdb;
-	$empty_array = array();
+	return $wpdb->get_results( $wpdb->prepare( "SELECT meta_key, meta_value, meta_id, term_id FROM $wpdb->termmeta WHERE term_id = %d ORDER BY meta_key,meta_id", $term_id ), ARRAY_A );
-	$single_taxonomy = ! is_array( $taxonomies ) || 1 === count( $taxonomies );
+}
-	if ( ! is_array( $taxonomies ) ) {
-		$taxonomies = array( $taxonomies );
+/**
-	}
+* Registers a meta key for terms.
+*
-	foreach ( $taxonomies as $taxonomy ) {
+* @since 4.9.8
-		if ( ! taxonomy_exists($taxonomy) ) {
+*
-			$error = new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));
+* @param string $taxonomy Taxonomy to register a meta key for. Pass an empty string
-			return $error;
+*                         to register the meta key across all existing taxonomies.
-		}
+* @param string $meta_key The meta key to register.
-	}
+* @param array  $args     Data used to describe the meta key when registered. See
+*                         {@see register_meta()} for a list of supported arguments.
-	$defaults = array('orderby' => 'name', 'order' => 'ASC',
+* @return bool True if the meta key was successfully registered, false if not.
-		'hide_empty' => true, 'exclude' => array(), 'exclude_tree' => array(), 'include' => array(),
+*/
-		'number' => '', 'fields' => 'all', 'name' => '', 'slug' => '', 'parent' => '', 'childless' => false,
+function register_term_meta( $taxonomy, $meta_key, array $args ) {
-		'hierarchical' => true, 'child_of' => 0, 'get' => '', 'name__like' => '', 'description__like' => '',
+	$args['object_subtype'] = $taxonomy;
-		'pad_counts' => false, 'offset' => '', 'search' => '', 'cache_domain' => 'core' );
-	$args = wp_parse_args( $args, $defaults );
+	return register_meta( 'term', $meta_key, $args );
-	$args['number'] = absint( $args['number'] );
+}
-	$args['offset'] = absint( $args['offset'] );
+/**
-	// Save queries by not crawling the tree in the case of multiple taxes or a flat tax.
+* Unregisters a meta key for terms.
-	$has_hierarchical_tax = false;
+*
-	foreach ( $taxonomies as $_tax ) {
+* @since 4.9.8
-		if ( is_taxonomy_hierarchical( $_tax ) ) {
+*
-			$has_hierarchical_tax = true;
+* @param string $taxonomy Taxonomy the meta key is currently registered for. Pass
-		}
+*                         an empty string if the meta key is registered across all
-	}
+*                         existing taxonomies.
+* @param string $meta_key The meta key to unregister.
-	if ( ! $has_hierarchical_tax ) {
+* @return bool True on success, false if the meta key was not previously registered.
-		$args['hierarchical'] = false;
+*/
-		$args['pad_counts'] = false;
+function unregister_term_meta( $taxonomy, $meta_key ) {
-	}
+	return unregister_meta_key( 'term', $meta_key, $taxonomy );
-	// 'parent' overrides 'child_of'.
-	if ( 0 < intval( $args['parent'] ) ) {
-		$args['child_of'] = false;
-	}
-	if ( 'all' == $args['get'] ) {
-		$args['childless'] = false;
-		$args['child_of'] = 0;
-		$args['hide_empty'] = 0;
-		$args['hierarchical'] = false;
-		$args['pad_counts'] = false;
-	}
-	/**
-	 * Filter the terms query arguments.
-	 *
-	 * @since 3.1.0
-	 *
-	 * @param array $args       An array of arguments.
-	 * @param array $taxonomies An array of taxonomies.
-	 */
-	$args = apply_filters( 'get_terms_args', $args, $taxonomies );
-	// Avoid the query if the queried parent/child_of term has no descendants.
-	$child_of = $args['child_of'];
-	$parent   = $args['parent'];
-	if ( $child_of ) {
-		$_parent = $child_of;
-	} elseif ( $parent ) {
-		$_parent = $parent;
-	} else {
-		$_parent = false;
-	}
-	if ( $_parent ) {
-		$in_hierarchy = false;
-		foreach ( $taxonomies as $_tax ) {
-			$hierarchy = _get_term_hierarchy( $_tax );
-			if ( isset( $hierarchy[ $_parent ] ) ) {
-				$in_hierarchy = true;
-			}
-		}
-		if ( ! $in_hierarchy ) {
-			return $empty_array;
-		}
-	}
-	// $args can be whatever, only use the args defined in defaults to compute the key
-	$filter_key = ( has_filter('list_terms_exclusions') ) ? serialize($GLOBALS['wp_filter']['list_terms_exclusions']) : '';
-	$key = md5( serialize( wp_array_slice_assoc( $args, array_keys( $defaults ) ) ) . serialize( $taxonomies ) . $filter_key );
-	$last_changed = wp_cache_get( 'last_changed', 'terms' );
-	if ( ! $last_changed ) {
-		$last_changed = microtime();
-		wp_cache_set( 'last_changed', $last_changed, 'terms' );
-	}
-	$cache_key = "get_terms:$key:$last_changed";
-	$cache = wp_cache_get( $cache_key, 'terms' );
-	if ( false !== $cache ) {
-		/**
-		 * Filter the given taxonomy's terms cache.
-		 *
-		 * @since 2.3.0
-		 *
-		 * @param array $cache      Cached array of terms for the given taxonomy.
-		 * @param array $taxonomies An array of taxonomies.
-		 * @param array $args       An array of arguments to get terms.
-		 */
-		$cache = apply_filters( 'get_terms', $cache, $taxonomies, $args );
-		return $cache;
-	}
-	$_orderby = strtolower( $args['orderby'] );
-	if ( 'count' == $_orderby ) {
-		$orderby = 'tt.count';
-	} elseif ( 'name' == $_orderby ) {
-		$orderby = 't.name';
-	} elseif ( 'slug' == $_orderby ) {
-		$orderby = 't.slug';
-	} elseif ( 'include' == $_orderby && ! empty( $args['include'] ) ) {
-		$include = implode( ',', array_map( 'absint', $args['include'] ) );
-		$orderby = "FIELD( t.term_id, $include )";
-	} elseif ( 'term_group' == $_orderby ) {
-		$orderby = 't.term_group';
-	} elseif ( 'description' == $_orderby ) {
-		$orderby = 'tt.description';
-	} elseif ( 'none' == $_orderby ) {
-		$orderby = '';
-	} elseif ( empty($_orderby) || 'id' == $_orderby ) {
-		$orderby = 't.term_id';
-	} else {
-		$orderby = 't.name';
-	}
-	/**
-	 * Filter the ORDERBY clause of the terms query.
-	 *
-	 * @since 2.8.0
-	 *
-	 * @param string $orderby    ORDERBY clause of the terms query.
-	 * @param array  $args       An array of terms query arguments.
-	 * @param array  $taxonomies An array of taxonomies.
-	 */
-	$orderby = apply_filters( 'get_terms_orderby', $orderby, $args, $taxonomies );
-	$order = strtoupper( $args['order'] );
-	if ( ! empty( $orderby ) ) {
-		$orderby = "ORDER BY $orderby";
-	} else {
-		$order = '';
-	}
-	if ( '' !== $order && ! in_array( $order, array( 'ASC', 'DESC' ) ) ) {
-		$order = 'ASC';
-	}
-	$where = "tt.taxonomy IN ('" . implode("', '", $taxonomies) . "')";
-	$exclude = $args['exclude'];
-	$exclude_tree = $args['exclude_tree'];
-	$include = $args['include'];
-	$inclusions = '';
-	if ( ! empty( $include ) ) {
-		$exclude = '';
-		$exclude_tree = '';
-		$inclusions = implode( ',', wp_parse_id_list( $include ) );
-	}
-	if ( ! empty( $inclusions ) ) {
-		$inclusions = ' AND t.term_id IN ( ' . $inclusions . ' )';
-		$where .= $inclusions;
-	}
-	$exclusions = array();
-	if ( ! empty( $exclude_tree ) ) {
-		$exclude_tree = wp_parse_id_list( $exclude_tree );
-		$excluded_children = $exclude_tree;
-		foreach ( $exclude_tree as $extrunk ) {
-			$excluded_children = array_merge(
-				$excluded_children,
-				(array) get_terms( $taxonomies[0], array( 'child_of' => intval( $extrunk ), 'fields' => 'ids', 'hide_empty' => 0 ) )
-			);
-		}
-		$exclusions = array_merge( $excluded_children, $exclusions );
-	}
-	if ( ! empty( $exclude ) ) {
-		$exclusions = array_merge( wp_parse_id_list( $exclude ), $exclusions );
-	}
-	// 'childless' terms are those without an entry in the flattened term hierarchy.
-	$childless = (bool) $args['childless'];
-	if ( $childless ) {
-		foreach ( $taxonomies as $_tax ) {
-			$term_hierarchy = _get_term_hierarchy( $_tax );
-			$exclusions = array_merge( array_keys( $term_hierarchy ), $exclusions );
-		}
-	}
-	if ( ! empty( $exclusions ) ) {
-		$exclusions = ' AND t.term_id NOT IN (' . implode( ',', array_map( 'intval', $exclusions ) ) . ')';
-	} else {
-		$exclusions = '';
-	}
-	/**
-	 * Filter the terms to exclude from the terms query.
-	 *
-	 * @since 2.3.0
-	 *
-	 * @param string $exclusions NOT IN clause of the terms query.
-	 * @param array  $args       An array of terms query arguments.
-	 * @param array  $taxonomies An array of taxonomies.
-	 */
-	$exclusions = apply_filters( 'list_terms_exclusions', $exclusions, $args, $taxonomies );
-	if ( ! empty( $exclusions ) ) {
-		$where .= $exclusions;
-	}
-	if ( ! empty( $args['name'] ) ) {
-		if ( is_array( $args['name'] ) ) {
-			$name = array_map( 'sanitize_text_field', $args['name'] );
-			$where .= " AND t.name IN ('" . implode( "', '", array_map( 'esc_sql', $name ) ) . "')";
-		} else {
-			$name = sanitize_text_field( $args['name'] );
-			$where .= $wpdb->prepare( " AND t.name = %s", $name );
-		}
-	}
-	if ( ! empty( $args['slug'] ) ) {
-		if ( is_array( $args['slug'] ) ) {
-			$slug = array_map( 'sanitize_title', $args['slug'] );
-			$where .= " AND t.slug IN ('" . implode( "', '", $slug ) . "')";
-		} else {
-			$slug = sanitize_title( $args['slug'] );
-			$where .= " AND t.slug = '$slug'";
-		}
-	}
-	if ( ! empty( $args['name__like'] ) ) {
-		$where .= $wpdb->prepare( " AND t.name LIKE %s", '%' . $wpdb->esc_like( $args['name__like'] ) . '%' );
-	}
-	if ( ! empty( $args['description__like'] ) ) {
-		$where .= $wpdb->prepare( " AND tt.description LIKE %s", '%' . $wpdb->esc_like( $args['description__like'] ) . '%' );
-	}
-	if ( '' !== $parent ) {
-		$parent = (int) $parent;
-		$where .= " AND tt.parent = '$parent'";
-	}
-	$hierarchical = $args['hierarchical'];
-	if ( 'count' == $args['fields'] ) {
-		$hierarchical = false;
-	}
-	if ( $args['hide_empty'] && !$hierarchical ) {
-		$where .= ' AND tt.count > 0';
-	}
-	$number = $args['number'];
-	$offset = $args['offset'];
-	// don't limit the query results when we have to descend the family tree
-	if ( $number && ! $hierarchical && ! $child_of && '' === $parent ) {
-		if ( $offset ) {
-			$limits = 'LIMIT ' . $offset . ',' . $number;
-		} else {
-			$limits = 'LIMIT ' . $number;
-		}
-	} else {
-		$limits = '';
-	}
-	if ( ! empty( $args['search'] ) ) {
-		$like = '%' . $wpdb->esc_like( $args['search'] ) . '%';
-		$where .= $wpdb->prepare( ' AND ((t.name LIKE %s) OR (t.slug LIKE %s))', $like, $like );
-	}
-	$selects = array();
-	switch ( $args['fields'] ) {
-		case 'all':
-			$selects = array( 't.*', 'tt.*' );
-			break;
-		case 'ids':
-		case 'id=>parent':
-			$selects = array( 't.term_id', 'tt.parent', 'tt.count', 'tt.taxonomy' );
-			break;
-		case 'names':
-			$selects = array( 't.term_id', 'tt.parent', 'tt.count', 't.name', 'tt.taxonomy' );
-			break;
-		case 'count':
-			$orderby = '';
-			$order = '';
-			$selects = array( 'COUNT(*)' );
-			break;
-		case 'id=>name':
-			$selects = array( 't.term_id', 't.name', 'tt.count', 'tt.taxonomy' );
-			break;
-		case 'id=>slug':
-			$selects = array( 't.term_id', 't.slug', 'tt.count', 'tt.taxonomy' );
-			break;
-	}
-	$_fields = $args['fields'];
-	/**
-	 * Filter the fields to select in the terms query.
-	 *
-	 * Field lists modified using this filter will only modify the term fields returned
-	 * by the function when the `$fields` parameter set to 'count' or 'all'. In all other
-	 * cases, the term fields in the results array will be determined by the `$fields`
-	 * parameter alone.
-	 *
-	 * Use of this filter can result in unpredictable behavior, and is not recommended.
-	 *
-	 * @since 2.8.0
-	 *
-	 * @param array $selects    An array of fields to select for the terms query.
-	 * @param array $args       An array of term query arguments.
-	 * @param array $taxonomies An array of taxonomies.
-	 */
-	$fields = implode( ', ', apply_filters( 'get_terms_fields', $selects, $args, $taxonomies ) );
-	$join = "INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id";
-	$pieces = array( 'fields', 'join', 'where', 'orderby', 'order', 'limits' );
-	/**
-	 * Filter the terms query SQL clauses.
-	 *
-	 * @since 3.1.0
-	 *
-	 * @param array $pieces     Terms query SQL clauses.
-	 * @param array $taxonomies An array of taxonomies.
-	 * @param array $args       An array of terms query arguments.
-	 */
-	$clauses = apply_filters( 'terms_clauses', compact( $pieces ), $taxonomies, $args );
-	$fields = isset( $clauses[ 'fields' ] ) ? $clauses[ 'fields' ] : '';
-	$join = isset( $clauses[ 'join' ] ) ? $clauses[ 'join' ] : '';
-	$where = isset( $clauses[ 'where' ] ) ? $clauses[ 'where' ] : '';
-	$orderby = isset( $clauses[ 'orderby' ] ) ? $clauses[ 'orderby' ] : '';
-	$order = isset( $clauses[ 'order' ] ) ? $clauses[ 'order' ] : '';
-	$limits = isset( $clauses[ 'limits' ] ) ? $clauses[ 'limits' ] : '';
-	$query = "SELECT $fields FROM $wpdb->terms AS t $join WHERE $where $orderby $order $limits";
-	if ( 'count' == $_fields ) {
-		$term_count = $wpdb->get_var($query);
-		return $term_count;
-	}
-	$terms = $wpdb->get_results($query);
-	if ( 'all' == $_fields ) {
-		update_term_cache( $terms );
-	}
-	if ( empty($terms) ) {
-		wp_cache_add( $cache_key, array(), 'terms', DAY_IN_SECONDS );
-		/** This filter is documented in wp-includes/taxonomy.php */
-		$terms = apply_filters( 'get_terms', array(), $taxonomies, $args );
-		return $terms;
-	}
-	if ( $child_of ) {
-		foreach ( $taxonomies as $_tax ) {
-			$children = _get_term_hierarchy( $_tax );
-			if ( ! empty( $children ) ) {
-				$terms = _get_term_children( $child_of, $terms, $_tax );
-			}
-		}
-	}
-	// Update term counts to include children.
-	if ( $args['pad_counts'] && 'all' == $_fields ) {
-		foreach ( $taxonomies as $_tax ) {
-			_pad_term_counts( $terms, $_tax );
-		}
-	}
-	// Make sure we show empty categories that have children.
-	if ( $hierarchical && $args['hide_empty'] && is_array( $terms ) ) {
-		foreach ( $terms as $k => $term ) {
-			if ( ! $term->count ) {
-				$children = get_term_children( $term->term_id, $term->taxonomy );
-				if ( is_array( $children ) ) {
-					foreach ( $children as $child_id ) {
-						$child = get_term( $child_id, $term->taxonomy );
-						if ( $child->count ) {
-							continue 2;
-						}
-					}
-				}
-				// It really is empty
-				unset($terms[$k]);
-			}
-		}
-	}
-	$_terms = array();
-	if ( 'id=>parent' == $_fields ) {
-		foreach ( $terms as $term ) {
-			$_terms[ $term->term_id ] = $term->parent;
-		}
-	} elseif ( 'ids' == $_fields ) {
-		foreach ( $terms as $term ) {
-			$_terms[] = $term->term_id;
-		}
-	} elseif ( 'names' == $_fields ) {
-		foreach ( $terms as $term ) {
-			$_terms[] = $term->name;
-		}
-	} elseif ( 'id=>name' == $_fields ) {
-		foreach ( $terms as $term ) {
-			$_terms[ $term->term_id ] = $term->name;
-		}
-	} elseif ( 'id=>slug' == $_fields ) {
-		foreach ( $terms as $term ) {
-			$_terms[ $term->term_id ] = $term->slug;
-		}
-	}
-	if ( ! empty( $_terms ) ) {
-		$terms = $_terms;
-	}
-	if ( $number && is_array( $terms ) && count( $terms ) > $number ) {
-		$terms = array_slice( $terms, $offset, $number );
-	}
-	wp_cache_add( $cache_key, $terms, 'terms', DAY_IN_SECONDS );
-	/** This filter is documented in wp-includes/taxonomy */
-	$terms = apply_filters( 'get_terms', $terms, $taxonomies, $args );
-	return $terms;
 }
 /**
 * Check if Term exists.
 *
 *
 * @since 3.0.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
-* @param int|string $term The term to check
+* @param int|string $term     The term to check. Accepts term ID, slug, or name.
-* @param string $taxonomy The taxonomy name to use
+* @param string     $taxonomy The taxonomy name to use
-* @param int $parent Optional. ID of parent term under which to confine the exists search.
+* @param int        $parent   Optional. ID of parent term under which to confine the exists search.
 * @return mixed Returns null if the term does not exist. Returns the term ID
 *               if no taxonomy is specified and the term ID exists. Returns
 *               an array of the term ID and the term taxonomy ID the taxonomy
 *               is specified and the pairing exists.
 */
 *
 * You can use either an id or the term object for both parameters.
 *
 * @since 3.4.0
 *
-* @param int|object $term1 ID or object to check if this is the parent term.
+* @param int|object $term1    ID or object to check if this is the parent term.
-* @param int|object $term2 The child term.
+* @param int|object $term2    The child term.
-* @param string $taxonomy Taxonomy name that $term1 and $term2 belong to.
+* @param string     $taxonomy Taxonomy name that $term1 and `$term2` belong to.
-* @return bool Whether $term2 is child of $term1
+* @return bool Whether `$term2` is a child of `$term1`.
 */
 function term_is_ancestor_of( $term1, $term2, $taxonomy ) {
 	if ( ! isset( $term1->term_id ) )
 		$term1 = get_term( $term1, $taxonomy );
 	if ( ! isset( $term2->parent ) )
 *
 * The $term is expected to be either an array or an object.
 *
 * @since 2.3.0
 *
-* @param array|object $term The term to check
+* @param array|object $term     The term to check.
-* @param string $taxonomy The taxonomy name to use
+* @param string       $taxonomy The taxonomy name to use.
-* @param string $context Default is 'display'.
+* @param string       $context  Optional. Context in which to sanitize the term. Accepts 'edit', 'db',
-* @return array|object Term with all fields sanitized
+*                               'display', 'attribute', or 'js'. Default 'display'.
+* @return array|object Term with all fields sanitized.
 */
 function sanitize_term($term, $taxonomy, $context = 'display') {
 	$fields = array( 'term_id', 'name', 'description', 'slug', 'count', 'parent', 'term_group', 'term_taxonomy_id', 'object_id' );
 	$do_object = is_object( $term );
 	$term_id = $do_object ? $term->term_id : (isset($term['term_id']) ? $term['term_id'] : 0);
 * without creating your own filter function. Simply create a function that
 * hooks into the filter you need.
 *
 * @since 2.3.0
 *
-* @global wpdb $wpdb WordPress database abstraction object.
+* @param string $field    Term field to sanitize.
-*
+* @param string $value    Search for this term value.
-* @param string $field Term field to sanitize
+* @param int    $term_id  Term ID.
-* @param string $value Search for this term value
+* @param string $taxonomy Taxonomy Name.
-* @param int $term_id Term ID
+* @param string $context  Context in which to sanitize the term field. Accepts 'edit', 'db', 'display',
-* @param string $taxonomy Taxonomy Name
+*                         'attribute', or 'js'.
-* @param string $context Either edit, db, display, attribute, or js.
+* @return mixed Sanitized field.
-* @return mixed sanitized field
 */
 function sanitize_term_field($field, $value, $term_id, $taxonomy, $context) {
 	$int_fields = array( 'parent', 'term_id', 'count', 'term_group', 'term_taxonomy_id', 'object_id' );
 	if ( in_array( $field, $int_fields ) ) {
 		$value = (int) $value;
 		return $value;
 	if ( 'edit' == $context ) {
 		/**
-		 * Filter a term field to edit before it is sanitized.
+		 * Filters a term field to edit before it is sanitized.
 		 *
 		 * The dynamic portion of the filter name, `$field`, refers to the term field.
 		 *
 		 * @since 2.3.0
 		 *
 		 * @param string $taxonomy Taxonomy slug.
 		 */
 		$value = apply_filters( "edit_term_{$field}", $value, $term_id, $taxonomy );
 		/**
-		 * Filter the taxonomy field to edit before it is sanitized.
+		 * Filters the taxonomy field to edit before it is sanitized.
 		 *
 		 * The dynamic portions of the filter name, `$taxonomy` and `$field`, refer
 		 * to the taxonomy slug and taxonomy field, respectively.
 		 *
 		 * @since 2.3.0
 		 *
 		 * @param mixed $value   Value of the taxonomy field to edit.
 		 * @param int   $term_id Term ID.
 		 */
 		$value = apply_filters( "edit_{$taxonomy}_{$field}", $value, $term_id );
 		if ( 'description' == $field )
 			$value = esc_html($value); // textarea_escaped
 		else
 			$value = esc_attr($value);
 	} elseif ( 'db' == $context ) {
 		/**
-		 * Filter a term field value before it is sanitized.
+		 * Filters a term field value before it is sanitized.
 		 *
 		 * The dynamic portion of the filter name, `$field`, refers to the term field.
 		 *
 		 * @since 2.3.0
 		 *
 		 * @param string $taxonomy Taxonomy slug.
 		 */
 		$value = apply_filters( "pre_term_{$field}", $value, $taxonomy );
 		/**
-		 * Filter a taxonomy field before it is sanitized.
+		 * Filters a taxonomy field before it is sanitized.
 		 *
 		 * The dynamic portions of the filter name, `$taxonomy` and `$field`, refer
 		 * to the taxonomy slug and field name, respectively.
 		 *
 		 * @since 2.3.0
 		 *
 		 * @param mixed $value Value of the taxonomy field.
 		 */
 		$value = apply_filters( "pre_{$taxonomy}_{$field}", $value );
 		// Back compat filters
 		if ( 'slug' == $field ) {
 			/**
-			 * Filter the category nicename before it is sanitized.
+			 * Filters the category nicename before it is sanitized.
 			 *
-			 * Use the pre_{$taxonomy}_{$field} hook instead.
+			 * Use the {@see 'pre_$taxonomy_$field'} hook instead.
 			 *
 			 * @since 2.0.3
 			 *
 			 * @param string $value The category nicename.
 			 */
 		}
 	} elseif ( 'rss' == $context ) {
 		/**
-		 * Filter the term field for use in RSS.
+		 * Filters the term field for use in RSS.
 		 *
 		 * The dynamic portion of the filter name, `$field`, refers to the term field.
 		 *
 		 * @since 2.3.0
 		 *
 		 * @param string $taxonomy Taxonomy slug.
 		 */
 		$value = apply_filters( "term_{$field}_rss", $value, $taxonomy );
 		/**
-		 * Filter the taxonomy field for use in RSS.
+		 * Filters the taxonomy field for use in RSS.
 		 *
-		 * The dynamic portions of the hook name, `$taxonomy`, and $field, refer
+		 * The dynamic portions of the hook name, `$taxonomy`, and `$field`, refer
 		 * to the taxonomy slug and field name, respectively.
 		 *
 		 * @since 2.3.0
 		 *
 		 * @param mixed $value Value of the taxonomy field.
 		$value = apply_filters( "{$taxonomy}_{$field}_rss", $value );
 	} else {
 		// Use display filters by default.
 		/**
-		 * Filter the term field sanitized for display.
+		 * Filters the term field sanitized for display.
 		 *
 		 * The dynamic portion of the filter name, `$field`, refers to the term field name.
 		 *
 		 * @since 2.3.0
 		 *
 		 * @param string $context  Context to retrieve the term field value.
 		 */
 		$value = apply_filters( "term_{$field}", $value, $term_id, $taxonomy, $context );
 		/**
-		 * Filter the taxonomy field sanitized for display.
+		 * Filters the taxonomy field sanitized for display.
 		 *
-		 * The dynamic portions of the filter name, `$taxonomy`, and $field, refer
+		 * The dynamic portions of the filter name, `$taxonomy`, and `$field`, refer
 		 * to the taxonomy slug and taxonomy field, respectively.
 		 *
 		 * @since 2.3.0
 		 *
 		 * @param mixed  $value   Value of the taxonomy field.
 *
 * Default $args is 'hide_empty' which can be 'hide_empty=true' or array('hide_empty' => true).
 *
 * @since 2.3.0
 *
-* @param string $taxonomy Taxonomy name
+* @param string       $taxonomy Taxonomy name.
-* @param array|string $args Overwrite defaults. See get_terms()
+* @param array|string $args     Optional. Array of arguments that get passed to get_terms().
-* @return int|WP_Error How many terms are in $taxonomy. WP_Error if $taxonomy does not exist.
+*                               Default empty array.
+* @return array|int|WP_Error Number of terms in that taxonomy or WP_Error if the taxonomy does not exist.
 */
 function wp_count_terms( $taxonomy, $args = array() ) {
 	$defaults = array('hide_empty' => false);
 	$args = wp_parse_args($args, $defaults);
-	// backwards compatibility
+	// backward compatibility
 	if ( isset($args['ignore_empty']) ) {
 		$args['hide_empty'] = $args['ignore_empty'];
 		unset($args['ignore_empty']);
 	}
 * a particular taxonomy or taxonomies. Does not remove the term or
 * taxonomy itself.
 *
 * @since 2.3.0
 *
-* @param int $object_id The term Object Id that refers to the term
+* @param int          $object_id  The term Object Id that refers to the term.
 * @param string|array $taxonomies List of Taxonomy Names or single Taxonomy name.
 */
 function wp_delete_object_term_relationships( $object_id, $taxonomies ) {
 	$object_id = (int) $object_id;
 * Removes a term from the database.
 *
 * If the term is a parent of other terms, then the children will be updated to
 * that term's parent.
 *
-* The $args 'default' will only override the terms found, if there is only one
+* Metadata associated with the term will be deleted.
-* term found. Any other and the found terms are used.
-*
-* The $args 'force_default' will force the term supplied as default to be
-* assigned even if the object was not going to be termless
 *
 * @since 2.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
-* @param int $term Term ID
+* @param int          $term     Term ID.
-* @param string $taxonomy Taxonomy Name
+* @param string       $taxonomy Taxonomy Name.
-* @param array|string $args Optional. Change 'default' term id and override found term ids.
+* @param array|string $args {
-* @return bool|WP_Error Returns false if not term; true if completes delete action.
+*     Optional. Array of arguments to override the default term ID. Default empty array.
+*
+*     @type int  $default       The term ID to make the default term. This will only override
+*                               the terms found if there is only one term found. Any other and
+*                               the found terms are used.
+*     @type bool $force_default Optional. Whether to force the supplied term as default to be
+*                               assigned even if the object was not going to be term-less.
+*                               Default false.
+* }
+* @return bool|int|WP_Error True on success, false if term does not exist. Zero on attempted
+*                           deletion of default Category. WP_Error if the taxonomy does not exist.
 */
 function wp_delete_term( $term, $taxonomy, $args = array() ) {
 	global $wpdb;
 	$term = (int) $term;
 		 * @since 2.9.0
 		 *
 		 * @param array $edit_tt_ids An array of term taxonomy IDs for the given term.
 		 */
 		do_action( 'edit_term_taxonomies', $edit_tt_ids );
 		$wpdb->update( $wpdb->term_taxonomy, compact( 'parent' ), array( 'parent' => $term_obj->term_id) + compact( 'taxonomy' ) );
 		// Clean the cache for all child terms.
 		$edit_term_ids = wp_list_pluck( $edit_ids, 'term_id' );
 		clean_term_cache( $edit_term_ids, $taxonomy );
 		 * @param array $edit_tt_ids An array of term taxonomy IDs for the given term.
 		 */
 		do_action( 'edited_term_taxonomies', $edit_tt_ids );
 	}
-	$objects = $wpdb->get_col( $wpdb->prepare( "SELECT object_id FROM $wpdb->term_relationships WHERE term_taxonomy_id = %d", $tt_id ) );
+	// Get the term before deleting it or its term relationships so we can pass to actions below.
+	$deleted_term = get_term( $term, $taxonomy );
-	foreach ( (array) $objects as $object ) {
-		$terms = wp_get_object_terms($object, $taxonomy, array('fields' => 'ids', 'orderby' => 'none'));
+	$object_ids = (array) $wpdb->get_col( $wpdb->prepare( "SELECT object_id FROM $wpdb->term_relationships WHERE term_taxonomy_id = %d", $tt_id ) );
+	foreach ( $object_ids as $object_id ) {
+		$terms = wp_get_object_terms( $object_id, $taxonomy, array( 'fields' => 'ids', 'orderby' => 'none' ) );
 		if ( 1 == count($terms) && isset($default) ) {
 			$terms = array($default);
 		} else {
 			$terms = array_diff($terms, array($term));
 			if (isset($default) && isset($force_default) && $force_default)
 				$terms = array_merge($terms, array($default));
 		}
 		$terms = array_map('intval', $terms);
-		wp_set_object_terms($object, $terms, $taxonomy);
+		wp_set_object_terms( $object_id, $terms, $taxonomy );
 	}
-	// Clean the relationship caches for all object types using this term
+	// Clean the relationship caches for all object types using this term.
 	$tax_object = get_taxonomy( $taxonomy );
 	foreach ( $tax_object->object_type as $object_type )
-		clean_object_term_cache( $objects, $object_type );
+		clean_object_term_cache( $object_ids, $object_type );
-	// Get the object before deletion so we can pass to actions below
+	$term_meta_ids = $wpdb->get_col( $wpdb->prepare( "SELECT meta_id FROM $wpdb->termmeta WHERE term_id = %d ", $term ) );
-	$deleted_term = get_term( $term, $taxonomy );
+	foreach ( $term_meta_ids as $mid ) {
+		delete_metadata_by_mid( 'term', $mid );
+	}
 	/**
 	 * Fires immediately before a term taxonomy ID is deleted.
 	 *
 	 * @since 2.9.0
 	/**
 	 * Fires after a term is deleted from the database and the cache is cleaned.
 	 *
 	 * @since 2.5.0
+	 * @since 4.5.0 Introduced the `$object_ids` argument.
 	 *
 	 * @param int     $term         Term ID.
 	 * @param int     $tt_id        Term taxonomy ID.
 	 * @param string  $taxonomy     Taxonomy slug.
 	 * @param mixed   $deleted_term Copy of the already-deleted term, in the form specified
 	 *                              by the parent function. WP_Error otherwise.
-	 */
+	 * @param array   $object_ids   List of term object IDs.
-	do_action( 'delete_term', $term, $tt_id, $taxonomy, $deleted_term );
+	 */
+	do_action( 'delete_term', $term, $tt_id, $taxonomy, $deleted_term, $object_ids );
 	/**
 	 * Fires after a term in a specific taxonomy is deleted.
 	 *
 	 * The dynamic portion of the hook name, `$taxonomy`, refers to the specific
 	 * taxonomy the term belonged to.
 	 *
 	 * @since 2.3.0
+	 * @since 4.5.0 Introduced the `$object_ids` argument.
 	 *
 	 * @param int     $term         Term ID.
 	 * @param int     $tt_id        Term taxonomy ID.
 	 * @param mixed   $deleted_term Copy of the already-deleted term, in the form specified
-	 *                              by the parent function. {@see WP_Error} otherwise.
+	 *                              by the parent function. WP_Error otherwise.
-	 */
+	 * @param array   $object_ids   List of term object IDs.
-	do_action( "delete_$taxonomy", $term, $tt_id, $deleted_term );
+	 */
+	do_action( "delete_{$taxonomy}", $term, $tt_id, $deleted_term, $object_ids );
 	return true;
 }
 /**
 * Deletes one existing category.
 *
 * @since 2.0.0
 *
-* @param int $cat_ID
+* @param int $cat_ID Category term ID.
-* @return mixed Returns true if completes delete action; false if term doesn't exist;
+* @return bool|int|WP_Error Returns true if completes delete action; false if term doesn't exist;
 * 	Zero on attempted deletion of default Category; WP_Error object is also a possibility.
 */
 function wp_delete_category( $cat_ID ) {
 	return wp_delete_term( $cat_ID, 'category' );
 }
 * Retrieves the terms associated with the given object(s), in the supplied taxonomies.
 *
 * @since 2.3.0
 * @since 4.2.0 Added support for 'taxonomy', 'parent', and 'term_taxonomy_id' values of `$orderby`.
 *              Introduced `$parent` argument.
-*
+* @since 4.4.0 Introduced `$meta_query` and `$update_term_meta_cache` arguments. When `$fields` is 'all' or
-* @global wpdb $wpdb WordPress database abstraction object.
+*              'all_with_object_id', an array of `WP_Term` objects will be returned.
+* @since 4.7.0 Refactored to use WP_Term_Query, and to support any WP_Term_Query arguments.
 *
 * @param int|array    $object_ids The ID(s) of the object(s) to retrieve.
 * @param string|array $taxonomies The taxonomies to retrieve terms from.
-* @param array|string $args {
+* @param array|string $args       See WP_Term_Query::__construct() for supported arguments.
-*     Array of arguments.
-*     @type string $orderby Field by which results should be sorted. Accepts 'name', 'count', 'slug', 'term_group',
-*                           'term_order', 'taxonomy', 'parent', or 'term_taxonomy_id'. Default 'name'.
-*     @type string $order   Sort order. Accepts 'ASC' or 'DESC'. Default 'ASC'.
-*     @type string $fields  Fields to return for matched terms. Accepts 'all', 'ids', 'names', and
-*                           'all_with_object_id'. Note that 'all' or 'all_with_object_id' will result in an array of
-*                           term objects being returned, 'ids' will return an array of integers, and 'names' an array
-*                           of strings.
-*     @type int    $parent  Optional. Limit results to the direct children of a given term ID.
-* }
 * @return array|WP_Error The requested term data or empty array if no terms found.
 *                        WP_Error if any of the $taxonomies don't exist.
 */
 function wp_get_object_terms($object_ids, $taxonomies, $args = array()) {
-	global $wpdb;
 	if ( empty( $object_ids ) || empty( $taxonomies ) )
 		return array();
 	if ( !is_array($taxonomies) )
 		$taxonomies = array($taxonomies);
 	foreach ( $taxonomies as $taxonomy ) {
 		if ( ! taxonomy_exists($taxonomy) )
-			return new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));
+			return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
 	}
 	if ( !is_array($object_ids) )
 		$object_ids = array($object_ids);
 	$object_ids = array_map('intval', $object_ids);
-	$defaults = array(
+	$args = wp_parse_args( $args );
-		'orderby' => 'name',
-		'order'   => 'ASC',
+	/**
-		'fields'  => 'all',
+	 * Filter arguments for retrieving object terms.
-		'parent'  => '',
+	 *
-	);
+	 * @since 4.9.0
-	$args = wp_parse_args( $args, $defaults );
+	 *
+	 * @param array        $args       An array of arguments for retrieving terms for the given object(s).
+	 *                                 See {@see wp_get_object_terms()} for details.
+	 * @param int|array    $object_ids Object ID or array of IDs.
+	 * @param string|array $taxonomies The taxonomies to retrieve terms from.
+	 */
+	$args = apply_filters( 'wp_get_object_terms_args', $args, $object_ids, $taxonomies );
+	/*
+	 * When one or more queried taxonomies is registered with an 'args' array,
+	 * those params override the `$args` passed to this function.
+	 */
 	$terms = array();
-	if ( count($taxonomies) > 1 ) {
+	if ( count( $taxonomies ) > 1 ) {
 		foreach ( $taxonomies as $index => $taxonomy ) {
-			$t = get_taxonomy($taxonomy);
+			$t = get_taxonomy( $taxonomy );
-			if ( isset($t->args) && is_array($t->args) && $args != array_merge($args, $t->args) ) {
+			if ( isset( $t->args ) && is_array( $t->args ) && $args != array_merge( $args, $t->args ) ) {
-				unset($taxonomies[$index]);
+				unset( $taxonomies[ $index ] );
-				$terms = array_merge($terms, wp_get_object_terms($object_ids, $taxonomy, array_merge($args, $t->args)));
+				$terms = array_merge( $terms, wp_get_object_terms( $object_ids, $taxonomy, array_merge( $args, $t->args ) ) );
 			}
 		}
 	} else {
-		$t = get_taxonomy($taxonomies[0]);
+		$t = get_taxonomy( $taxonomies[0] );
-		if ( isset($t->args) && is_array($t->args) )
+		if ( isset( $t->args ) && is_array( $t->args ) ) {
-			$args = array_merge($args, $t->args);
+			$args = array_merge( $args, $t->args );
-	}
+		}
+	}
-	$orderby = $args['orderby'];
-	$order = $args['order'];
+	$args['taxonomy'] = $taxonomies;
-	$fields = $args['fields'];
+	$args['object_ids'] = $object_ids;
-	if ( in_array( $orderby, array( 'term_id', 'name', 'slug', 'term_group' ) ) ) {
+	// Taxonomies registered without an 'args' param are handled here.
-		$orderby = "t.$orderby";
+	if ( ! empty( $taxonomies ) ) {
-	} else if ( in_array( $orderby, array( 'count', 'parent', 'taxonomy', 'term_taxonomy_id' ) ) ) {
+		$terms_from_remaining_taxonomies = get_terms( $args );
-		$orderby = "tt.$orderby";
-	} else if ( 'term_order' === $orderby ) {
+		// Array keys should be preserved for values of $fields that use term_id for keys.
-		$orderby = 'tr.term_order';
+		if ( ! empty( $args['fields'] ) && 0 === strpos( $args['fields'], 'id=>' ) ) {
-	} else if ( 'none' === $orderby ) {
+			$terms = $terms + $terms_from_remaining_taxonomies;
-		$orderby = '';
+		} else {
-		$order = '';
+			$terms = array_merge( $terms, $terms_from_remaining_taxonomies );
-	} else {
+		}
-		$orderby = 't.term_id';
-	}
-	// tt_ids queries can only be none or tr.term_taxonomy_id
-	if ( ('tt_ids' == $fields) && !empty($orderby) )
-		$orderby = 'tr.term_taxonomy_id';
-	if ( !empty($orderby) )
-		$orderby = "ORDER BY $orderby";
-	$order = strtoupper( $order );
-	if ( '' !== $order && ! in_array( $order, array( 'ASC', 'DESC' ) ) )
-		$order = 'ASC';
-	$taxonomy_array = $taxonomies;
-	$object_id_array = $object_ids;
-	$taxonomies = "'" . implode("', '", $taxonomies) . "'";
-	$object_ids = implode(', ', $object_ids);
-	$select_this = '';
-	if ( 'all' == $fields ) {
-		$select_this = 't.*, tt.*';
-	} elseif ( 'ids' == $fields ) {
-		$select_this = 't.term_id';
-	} elseif ( 'names' == $fields ) {
-		$select_this = 't.name';
-	} elseif ( 'slugs' == $fields ) {
-		$select_this = 't.slug';
-	} elseif ( 'all_with_object_id' == $fields ) {
-		$select_this = 't.*, tt.*, tr.object_id';
-	}
-	$where = array(
-		"tt.taxonomy IN ($taxonomies)",
-		"tr.object_id IN ($object_ids)",
-	);
-	if ( '' !== $args['parent'] ) {
-		$where[] = $wpdb->prepare( 'tt.parent = %d', $args['parent'] );
-	}
-	$where = implode( ' AND ', $where );
-	$query = "SELECT $select_this FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON tt.term_id = t.term_id INNER JOIN $wpdb->term_relationships AS tr ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE $where $orderby $order";
-	$objects = false;
-	if ( 'all' == $fields || 'all_with_object_id' == $fields ) {
-		$_terms = $wpdb->get_results( $query );
-		foreach ( $_terms as $key => $term ) {
-			$_terms[$key] = sanitize_term( $term, $taxonomy, 'raw' );
-		}
-		$terms = array_merge( $terms, $_terms );
-		update_term_cache( $terms );
-		$objects = true;
-	} elseif ( 'ids' == $fields || 'names' == $fields || 'slugs' == $fields ) {
-		$_terms = $wpdb->get_col( $query );
-		$_field = ( 'ids' == $fields ) ? 'term_id' : 'name';
-		foreach ( $_terms as $key => $term ) {
-			$_terms[$key] = sanitize_term_field( $_field, $term, $term, $taxonomy, 'raw' );
-		}
-		$terms = array_merge( $terms, $_terms );
-	} elseif ( 'tt_ids' == $fields ) {
-		$terms = $wpdb->get_col("SELECT tr.term_taxonomy_id FROM $wpdb->term_relationships AS tr INNER JOIN $wpdb->term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tr.object_id IN ($object_ids) AND tt.taxonomy IN ($taxonomies) $orderby $order");
-		foreach ( $terms as $key => $tt_id ) {
-			$terms[$key] = sanitize_term_field( 'term_taxonomy_id', $tt_id, 0, $taxonomy, 'raw' ); // 0 should be the term id, however is not needed when using raw context.
-		}
-	}
-	if ( ! $terms ) {
-		$terms = array();
-	} elseif ( $objects && 'all_with_object_id' !== $fields ) {
-		$_tt_ids = array();
-		$_terms = array();
-		foreach ( $terms as $term ) {
-			if ( in_array( $term->term_taxonomy_id, $_tt_ids ) ) {
-				continue;
-			}
-			$_tt_ids[] = $term->term_taxonomy_id;
-			$_terms[] = $term;
-		}
-		$terms = $_terms;
-	} elseif ( ! $objects ) {
-		$terms = array_values( array_unique( $terms ) );
 	}
 	/**
-	 * Filter the terms for a given object or objects.
+	 * Filters the terms for a given object or objects.
 	 *
 	 * @since 4.2.0
 	 *
-	 * @param array $terms           An array of terms for the given object or objects.
+	 * @param array $terms      An array of terms for the given object or objects.
-	 * @param array $object_id_array Array of object IDs for which `$terms` were retrieved.
+	 * @param array $object_ids Array of object IDs for which `$terms` were retrieved.
-	 * @param array $taxonomy_array  Array of taxonomies from which `$terms` were retrieved.
+	 * @param array $taxonomies Array of taxonomies from which `$terms` were retrieved.
-	 * @param array $args            An array of arguments for retrieving terms for the given
+	 * @param array $args       An array of arguments for retrieving terms for the given
-	 *                               object(s). See wp_get_object_terms() for details.
+	 *                          object(s). See wp_get_object_terms() for details.
 	 */
-	$terms = apply_filters( 'get_object_terms', $terms, $object_id_array, $taxonomy_array, $args );
+	$terms = apply_filters( 'get_object_terms', $terms, $object_ids, $taxonomies, $args );
+	$object_ids = implode( ',', $object_ids );
+	$taxonomies = "'" . implode( "', '", array_map( 'esc_sql', $taxonomies ) ) . "'";
 	/**
-	 * Filter the terms for a given object or objects.
+	 * Filters the terms for a given object or objects.
 	 *
 	 * The `$taxonomies` parameter passed to this filter is formatted as a SQL fragment. The
 	 * {@see 'get_object_terms'} filter is recommended as an alternative.
 	 *
 	 * @since 2.8.0
 	 *
 	 * @param array     $terms      An array of terms for the given object or objects.
 	 * @param int|array $object_ids Object ID or array of IDs.
 	 * @param string    $taxonomies SQL-formatted (comma-separated and quoted) list of taxonomy names.
 	 * @param array     $args       An array of arguments for retrieving terms for the given object(s).
-	 *                              See {@see wp_get_object_terms()} for details.
+	 *                              See wp_get_object_terms() for details.
 	 */
 	return apply_filters( 'wp_get_object_terms', $terms, $object_ids, $taxonomies, $args );
 }
 /**
 * is invalid. If it is not a valid, existing term, it is added and the term_id
 * is given.
 *
 * If the taxonomy is hierarchical, and the 'parent' argument is not empty,
 * the term is inserted and the term_id will be given.
+*
 * Error handling:
 * If $taxonomy does not exist or $term is empty,
 * a WP_Error object will be returned.
 *
 * If the term already exists on the same hierarchical level,
 * or the term slug and name are not unique, a WP_Error object will be returned.
 *
 * @global wpdb $wpdb WordPress database abstraction object.
+*
 * @since 2.3.0
 *
 * @param string       $term     The term to add or update.
 * @param string       $taxonomy The taxonomy to which to add the term.
 * @param array|string $args {
 *     @type string $description The term description. Default empty string.
 *     @type int    $parent      The id of the parent term. Default 0.
 *     @type string $slug        The term slug to use. Default empty string.
 * }
 * @return array|WP_Error An array containing the `term_id` and `term_taxonomy_id`,
-*                        {@see WP_Error} otherwise.
+*                        WP_Error otherwise.
 */
 function wp_insert_term( $term, $taxonomy, $args = array() ) {
 	global $wpdb;
 	if ( ! taxonomy_exists($taxonomy) ) {
-		return new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));
+		return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
 	}
 	/**
-	 * Filter a term before it is sanitized and inserted into the database.
+	 * Filters a term before it is sanitized and inserted into the database.
 	 *
 	 * @since 3.0.0
 	 *
 	 * @param string $term     The term to add or update.
 	 * @param string $taxonomy Taxonomy slug.
 	 */
 	$term = apply_filters( 'pre_insert_term', $term, $taxonomy );
 	if ( is_wp_error( $term ) ) {
 		return $term;
 	}
-	if ( is_int($term) && 0 == $term ) {
+	if ( is_int( $term ) && 0 == $term ) {
-		return new WP_Error('invalid_term_id', __('Invalid term ID'));
+		return new WP_Error( 'invalid_term_id', __( 'Invalid term ID.' ) );
 	}
-	if ( '' == trim($term) ) {
+	if ( '' == trim( $term ) ) {
-		return new WP_Error('empty_term_name', __('A name is required for this term'));
+		return new WP_Error( 'empty_term_name', __( 'A name is required for this term.' ) );
 	}
 	$defaults = array( 'alias_of' => '', 'description' => '', 'parent' => 0, 'slug' => '');
 	$args = wp_parse_args( $args, $defaults );
 	if ( $args['parent'] > 0 && ! term_exists( (int) $args['parent'] ) ) {
 		return new WP_Error( 'missing_parent', __( 'Parent term does not exist.' ) );
 	}
 	$args['name'] = $term;
 	$args['taxonomy'] = $taxonomy;
+	// Coerce null description to strings, to avoid database errors.
+	$args['description'] = (string) $args['description'];
 	$args = sanitize_term($args, $taxonomy, 'db');
 	// expected_slashed ($name)
 	$name = wp_unslash( $args['name'] );
 	$description = wp_unslash( $args['description'] );
 	/*
 	 * Prevent the creation of terms with duplicate names at the same level of a taxonomy hierarchy,
 	 * unless a unique slug has been explicitly provided.
 	 */
-	if ( $name_match = get_term_by( 'name', $name, $taxonomy ) ) {
+	$name_matches = get_terms( $taxonomy, array(
+		'name' => $name,
+		'hide_empty' => false,
+		'parent' => $args['parent'],
+	) );
+	/*
+	 * The `name` match in `get_terms()` doesn't differentiate accented characters,
+	 * so we do a stricter comparison here.
+	 */
+	$name_match = null;
+	if ( $name_matches ) {
+		foreach ( $name_matches as $_match ) {
+			if ( strtolower( $name ) === strtolower( $_match->name ) ) {
+				$name_match = $_match;
+				break;
+			}
+		}
+	}
+	if ( $name_match ) {
 		$slug_match = get_term_by( 'slug', $slug, $taxonomy );
 		if ( ! $slug_provided || $name_match->slug === $slug || $slug_match ) {
 			if ( is_taxonomy_hierarchical( $taxonomy ) ) {
 				$siblings = get_terms( $taxonomy, array( 'get' => 'all', 'parent' => $parent ) );
 				$existing_term = null;
-				if ( $name_match->slug === $slug && in_array( $name, wp_list_pluck( $siblings, 'name' ) ) ) {
+				if ( ( ! $slug_provided || $name_match->slug === $slug ) && in_array( $name, wp_list_pluck( $siblings, 'name' ) ) ) {
 					$existing_term = $name_match;
 				} elseif ( $slug_match && in_array( $slug, wp_list_pluck( $siblings, 'slug' ) ) ) {
 					$existing_term = $slug_match;
 				}
 				if ( $existing_term ) {
-					return new WP_Error( 'term_exists', __( 'A term with the name already exists with this parent.' ), $existing_term->term_id );
+					return new WP_Error( 'term_exists', __( 'A term with the name provided already exists with this parent.' ), $existing_term->term_id );
 				}
 			} else {
-				return new WP_Error( 'term_exists', __( 'A term with the name already exists in this taxonomy.' ), $name_match->term_id );
+				return new WP_Error( 'term_exists', __( 'A term with the name provided already exists in this taxonomy.' ), $name_match->term_id );
 			}
 		}
 	}
 	$slug = wp_unique_term_slug( $slug, (object) $args );
-	if ( false === $wpdb->insert( $wpdb->terms, compact( 'name', 'slug', 'term_group' ) ) ) {
+	$data = compact( 'name', 'slug', 'term_group' );
-		return new WP_Error( 'db_insert_error', __( 'Could not insert term into the database' ), $wpdb->last_error );
+	/**
+	 * Filters term data before it is inserted into the database.
+	 *
+	 * @since 4.7.0
+	 *
+	 * @param array  $data     Term data to be inserted.
+	 * @param string $taxonomy Taxonomy slug.
+	 * @param array  $args     Arguments passed to wp_insert_term().
+	 */
+	$data = apply_filters( 'wp_insert_term_data', $data, $taxonomy, $args );
+	if ( false === $wpdb->insert( $wpdb->terms, $data ) ) {
+		return new WP_Error( 'db_insert_error', __( 'Could not insert term into the database.' ), $wpdb->last_error );
 	}
 	$term_id = (int) $wpdb->insert_id;
 	// Seems unreachable, However, Is used in the case that a term name is provided, which sanitizes to an empty string.
 	 * @since 2.3.0
 	 *
 	 * @param int $term_id Term ID.
 	 * @param int $tt_id   Term taxonomy ID.
 	 */
-	do_action( "create_$taxonomy", $term_id, $tt_id );
+	do_action( "create_{$taxonomy}", $term_id, $tt_id );
 	/**
-	 * Filter the term ID after a new term is created.
+	 * Filters the term ID after a new term is created.
 	 *
 	 * @since 2.3.0
 	 *
 	 * @param int $term_id Term ID.
 	 * @param int $tt_id   Taxonomy term ID.
 	/**
 	 * Fires after a new term is created, and after the term cache has been cleaned.
 	 *
 	 * @since 2.3.0
-	 */
+	 *
-	do_action( "created_term", $term_id, $tt_id, $taxonomy );
+	 * @param int    $term_id  Term ID.
+	 * @param int    $tt_id    Term taxonomy ID.
+	 * @param string $taxonomy Taxonomy slug.
+	 */
+	do_action( 'created_term', $term_id, $tt_id, $taxonomy );
 	/**
 	 * Fires after a new term in a specific taxonomy is created, and after the term
 	 * cache has been cleaned.
 	 *
+	 * The dynamic portion of the hook name, `$taxonomy`, refers to the taxonomy slug.
+	 *
 	 * @since 2.3.0
 	 *
 	 * @param int $term_id Term ID.
 	 * @param int $tt_id   Term taxonomy ID.
 	 */
-	do_action( "created_$taxonomy", $term_id, $tt_id );
+	do_action( "created_{$taxonomy}", $term_id, $tt_id );
 	return array('term_id' => $term_id, 'term_taxonomy_id' => $tt_id);
 }
 /**
 * A term has no meaning until it is given context by defining which taxonomy it
 * exists under.
 *
 * @since 2.3.0
 *
+* @global wpdb $wpdb The WordPress database abstraction object.
+*
 * @param int              $object_id The object to relate to.
-* @param array|int|string $terms     A single term slug, single term id, or array of either term slugs or ids.
+* @param string|int|array $terms     A single term slug, single term id, or array of either term slugs or ids.
-*                                    Will replace all existing related terms in this taxonomy.
+*                                    Will replace all existing related terms in this taxonomy. Passing an
+*                                    empty value will remove all related terms.
 * @param string           $taxonomy  The context in which to relate the term to the object.
 * @param bool             $append    Optional. If false will delete difference of terms. Default false.
-* @return array|WP_Error Affected Term IDs.
+* @return array|WP_Error Term taxonomy IDs of the affected terms.
 */
 function wp_set_object_terms( $object_id, $terms, $taxonomy, $append = false ) {
 	global $wpdb;
 	$object_id = (int) $object_id;
-	if ( ! taxonomy_exists($taxonomy) )
+	if ( ! taxonomy_exists( $taxonomy ) ) {
-		return new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));
+		return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
+	}
 	if ( !is_array($terms) )
 		$terms = array($terms);
 	if ( ! $append )
 		/**
 		 * Fires immediately before an object-term relationship is added.
 		 *
 		 * @since 2.9.0
+		 * @since 4.7.0 Added the `$taxonomy` parameter.
 		 *
-		 * @param int $object_id Object ID.
+		 * @param int    $object_id Object ID.
-		 * @param int $tt_id     Term taxonomy ID.
+		 * @param int    $tt_id     Term taxonomy ID.
+		 * @param string $taxonomy  Taxonomy slug.
 		 */
-		do_action( 'add_term_relationship', $object_id, $tt_id );
+		do_action( 'add_term_relationship', $object_id, $tt_id, $taxonomy );
 		$wpdb->insert( $wpdb->term_relationships, array( 'object_id' => $object_id, 'term_taxonomy_id' => $tt_id ) );
 		/**
 		 * Fires immediately after an object-term relationship is added.
 		 *
 		 * @since 2.9.0
+		 * @since 4.7.0 Added the `$taxonomy` parameter.
 		 *
-		 * @param int $object_id Object ID.
+		 * @param int    $object_id Object ID.
-		 * @param int $tt_id     Term taxonomy ID.
+		 * @param int    $tt_id     Term taxonomy ID.
+		 * @param string $taxonomy  Taxonomy slug.
 		 */
-		do_action( 'added_term_relationship', $object_id, $tt_id );
+		do_action( 'added_term_relationship', $object_id, $tt_id, $taxonomy );
 		$new_tt_ids[] = $tt_id;
 	}
 	if ( $new_tt_ids )
 		wp_update_term_count( $new_tt_ids, $taxonomy );
 		foreach ( $tt_ids as $tt_id )
 			if ( in_array($tt_id, $final_tt_ids) )
 				$values[] = $wpdb->prepare( "(%d, %d, %d)", $object_id, $tt_id, ++$term_order);
 		if ( $values )
 			if ( false === $wpdb->query( "INSERT INTO $wpdb->term_relationships (object_id, term_taxonomy_id, term_order) VALUES " . join( ',', $values ) . " ON DUPLICATE KEY UPDATE term_order = VALUES(term_order)" ) )
-				return new WP_Error( 'db_insert_error', __( 'Could not insert term relationship into the database' ), $wpdb->last_error );
+				return new WP_Error( 'db_insert_error', __( 'Could not insert term relationship into the database.' ), $wpdb->last_error );
 	}
 	wp_cache_delete( $object_id, $taxonomy . '_relationships' );
+	wp_cache_delete( 'last_changed', 'terms' );
 	/**
 	 * Fires after an object's terms have been set.
 	 *
 	 * @since 2.8.0
 /**
 * Add term(s) associated with a given object.
 *
 * @since 3.6.0
 *
-* @param int $object_id The ID of the object to which the terms will be added.
+* @param int              $object_id The ID of the object to which the terms will be added.
-* @param array|int|string $terms The slug(s) or ID(s) of the term(s) to add.
+* @param string|int|array $terms     The slug(s) or ID(s) of the term(s) to add.
-* @param array|string $taxonomy Taxonomy name.
+* @param array|string     $taxonomy  Taxonomy name.
-* @return array|WP_Error Affected Term IDs
+* @return array|WP_Error Term taxonomy IDs of the affected terms.
 */
 function wp_add_object_terms( $object_id, $terms, $taxonomy ) {
 	return wp_set_object_terms( $object_id, $terms, $taxonomy, true );
 }
 *
 * @since 3.6.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
-* @param int $object_id The ID of the object from which the terms will be removed.
+* @param int              $object_id The ID of the object from which the terms will be removed.
-* @param array|int|string $terms The slug(s) or ID(s) of the term(s) to remove.
+* @param string|int|array $terms     The slug(s) or ID(s) of the term(s) to remove.
-* @param array|string $taxonomy Taxonomy name.
+* @param array|string     $taxonomy  Taxonomy name.
 * @return bool|WP_Error True on success, false or WP_Error on failure.
 */
 function wp_remove_object_terms( $object_id, $terms, $taxonomy ) {
 	global $wpdb;
 	$object_id = (int) $object_id;
 	if ( ! taxonomy_exists( $taxonomy ) ) {
-		return new WP_Error( 'invalid_taxonomy', __( 'Invalid Taxonomy' ) );
+		return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
 	}
 	if ( ! is_array( $terms ) ) {
 		$terms = array( $terms );
 	}
 		/**
 		 * Fires immediately before an object-term relationship is deleted.
 		 *
 		 * @since 2.9.0
+		 * @since 4.7.0 Added the `$taxonomy` parameter.
 		 *
 		 * @param int   $object_id Object ID.
 		 * @param array $tt_ids    An array of term taxonomy IDs.
+		 * @param string $taxonomy  Taxonomy slug.
 		 */
-		do_action( 'delete_term_relationships', $object_id, $tt_ids );
+		do_action( 'delete_term_relationships', $object_id, $tt_ids, $taxonomy );
 		$deleted = $wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->term_relationships WHERE object_id = %d AND term_taxonomy_id IN ($in_tt_ids)", $object_id ) );
+		wp_cache_delete( $object_id, $taxonomy . '_relationships' );
+		wp_cache_delete( 'last_changed', 'terms' );
 		/**
 		 * Fires immediately after an object-term relationship is deleted.
 		 *
 		 * @since 2.9.0
+		 * @since 4.7.0 Added the `$taxonomy` parameter.
 		 *
-		 * @param int   $object_id Object ID.
+		 * @param int    $object_id Object ID.
-		 * @param array $tt_ids    An array of term taxonomy IDs.
+		 * @param array  $tt_ids    An array of term taxonomy IDs.
+		 * @param string $taxonomy  Taxonomy slug.
 		 */
-		do_action( 'deleted_term_relationships', $object_id, $tt_ids );
+		do_action( 'deleted_term_relationships', $object_id, $tt_ids, $taxonomy );
 		wp_update_term_count( $tt_ids, $taxonomy );
 		return (bool) $deleted;
 	}
 }
 /**
 * Will make slug unique, if it isn't already.
 *
-* The $slug has to be unique global to every taxonomy, meaning that one
+* The `$slug` has to be unique global to every taxonomy, meaning that one
 * taxonomy term can't have a matching slug with another taxonomy term. Each
 * slug has to be globally unique for every taxonomy.
 *
 * The way this works is that if the taxonomy that the term belongs to is
 * hierarchical and has a parent, it will append that parent to the $slug.
 *
 * If that still doesn't return an unique slug, then it try to append a number
 * until it finds a number that is truly unique.
 *
-* The only purpose for $term is for appending a parent, if one exists.
+* The only purpose for `$term` is for appending a parent, if one exists.
 *
 * @since 2.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
-* @param string $slug The string that will be tried for a unique slug
+* @param string $slug The string that will be tried for a unique slug.
-* @param object $term The term object that the $slug will belong too
+* @param object $term The term object that the `$slug` will belong to.
 * @return string Will return a true unique slug.
 */
-function wp_unique_term_slug($slug, $term) {
+function wp_unique_term_slug( $slug, $term ) {
 	global $wpdb;
-	if ( ! term_exists( $slug ) )
+	$needs_suffix = true;
-		return $slug;
+	$original_slug = $slug;
 	// As of 4.1, duplicate slugs are allowed as long as they're in different taxonomies.
-	if ( get_option( 'db_version' ) >= 30133 && ! get_term_by( 'slug', $slug, $term->taxonomy ) ) {
+	if ( ! term_exists( $slug ) || get_option( 'db_version' ) >= 30133 && ! get_term_by( 'slug', $slug, $term->taxonomy ) ) {
-		return $slug;
+		$needs_suffix = false;
 	}
-	// If the taxonomy supports hierarchy and the term has a parent, make the slug unique
+	/*
-	// by incorporating parent slugs.
+	 * If the taxonomy supports hierarchy and the term has a parent, make the slug unique
-	if ( is_taxonomy_hierarchical($term->taxonomy) && !empty($term->parent) ) {
+	 * by incorporating parent slugs.
+	 */
+	$parent_suffix = '';
+	if ( $needs_suffix && is_taxonomy_hierarchical( $term->taxonomy ) && ! empty( $term->parent ) ) {
 		$the_parent = $term->parent;
 		while ( ! empty($the_parent) ) {
 			$parent_term = get_term($the_parent, $term->taxonomy);
 			if ( is_wp_error($parent_term) || empty($parent_term) )
 				break;
-			$slug .= '-' . $parent_term->slug;
+			$parent_suffix .= '-' . $parent_term->slug;
-			if ( ! term_exists( $slug ) )
+			if ( ! term_exists( $slug . $parent_suffix ) ) {
-				return $slug;
+				break;
+			}
 			if ( empty($parent_term->parent) )
 				break;
 			$the_parent = $parent_term->parent;
 		}
 	}
 	// If we didn't get a unique slug, try appending a number to make it unique.
-	if ( ! empty( $term->term_id ) )
-		$query = $wpdb->prepare( "SELECT slug FROM $wpdb->terms WHERE slug = %s AND term_id != %d", $slug, $term->term_id );
+	/**
-	else
+	 * Filters whether the proposed unique term slug is bad.
-		$query = $wpdb->prepare( "SELECT slug FROM $wpdb->terms WHERE slug = %s", $slug );
+	 *
+	 * @since 4.3.0
-	if ( $wpdb->get_var( $query ) ) {
+	 *
-		$num = 2;
+	 * @param bool   $needs_suffix Whether the slug needs to be made unique with a suffix.
-		do {
+	 * @param string $slug         The slug.
-			$alt_slug = $slug . "-$num";
+	 * @param object $term         Term object.
-			$num++;
+	 */
-			$slug_check = $wpdb->get_var( $wpdb->prepare( "SELECT slug FROM $wpdb->terms WHERE slug = %s", $alt_slug ) );
+	if ( apply_filters( 'wp_unique_term_slug_is_bad_slug', $needs_suffix, $slug, $term ) ) {
-		} while ( $slug_check );
+		if ( $parent_suffix ) {
-		$slug = $alt_slug;
+			$slug .= $parent_suffix;
-	}
+		} else {
+			if ( ! empty( $term->term_id ) )
-	return $slug;
+				$query = $wpdb->prepare( "SELECT slug FROM $wpdb->terms WHERE slug = %s AND term_id != %d", $slug, $term->term_id );
+			else
+				$query = $wpdb->prepare( "SELECT slug FROM $wpdb->terms WHERE slug = %s", $slug );
+			if ( $wpdb->get_var( $query ) ) {
+				$num = 2;
+				do {
+					$alt_slug = $slug . "-$num";
+					$num++;
+					$slug_check = $wpdb->get_var( $wpdb->prepare( "SELECT slug FROM $wpdb->terms WHERE slug = %s", $alt_slug ) );
+				} while ( $slug_check );
+				$slug = $alt_slug;
+			}
+		}
+	}
+	/**
+	 * Filters the unique term slug.
+	 *
+	 * @since 4.3.0
+	 *
+	 * @param string $slug          Unique term slug.
+	 * @param object $term          Term object.
+	 * @param string $original_slug Slug originally passed to the function for testing.
+	 */
+	return apply_filters( 'wp_unique_term_slug', $slug, $term, $original_slug );
 }
 /**
 * Update term based on arguments provided.
 *
 * If the 'slug' argument in $args is missing, then the 'name' in $args will be
 * used. It should also be noted that if you set 'slug' and it isn't unique then
 * a WP_Error will be passed back. If you don't pass any slug, then a unique one
 * will be created for you.
 *
-* For what can be overrode in $args, check the term scheme can contain and stay
+* For what can be overrode in `$args`, check the term scheme can contain and stay
 * away from the term keys.
 *
 * @since 2.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
-* @param int $term_id The ID of the term
+* @param int          $term_id  The ID of the term
-* @param string $taxonomy The context in which to relate the term to the object.
+* @param string       $taxonomy The context in which to relate the term to the object.
-* @param array|string $args Overwrite term field values
+* @param array|string $args     Optional. Array of get_terms() arguments. Default empty array.
 * @return array|WP_Error Returns Term ID and Taxonomy Term ID
 */
 function wp_update_term( $term_id, $taxonomy, $args = array() ) {
 	global $wpdb;
 	if ( ! taxonomy_exists( $taxonomy ) ) {
-		return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy' ) );
+		return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
 	}
 	$term_id = (int) $term_id;
 	// First, get all of the original args
-	$term = get_term( $term_id, $taxonomy, ARRAY_A );
+	$term = get_term( $term_id, $taxonomy );
 	if ( is_wp_error( $term ) ) {
 		return $term;
 	}
 	if ( ! $term ) {
-		return new WP_Error( 'invalid_term', __( 'Empty Term' ) );
+		return new WP_Error( 'invalid_term', __( 'Empty Term.' ) );
 	}
+	$term = (array) $term->data;
 	// Escape data pulled from DB.
-	$term = wp_slash($term);
+	$term = wp_slash( $term );
 	// Merge old and new args with new args overwriting old ones.
 	$args = array_merge($term, $args);
 	$defaults = array( 'alias_of' => '', 'description' => '', 'parent' => 0, 'slug' => '');
 	$description = wp_unslash( $args['description'] );
 	$parsed_args['name'] = $name;
 	$parsed_args['description'] = $description;
-	if ( '' == trim($name) )
+	if ( '' == trim( $name ) ) {
-		return new WP_Error('empty_term_name', __('A name is required for this term'));
+		return new WP_Error( 'empty_term_name', __( 'A name is required for this term.' ) );
+	}
 	if ( $parsed_args['parent'] > 0 && ! term_exists( (int) $parsed_args['parent'] ) ) {
 		return new WP_Error( 'missing_parent', __( 'Parent term does not exist.' ) );
 	}
 		$parsed_args['term_group'] = $term_group;
 	}
 	/**
-	 * Filter the term parent.
+	 * Filters the term parent.
 	 *
 	 * Hook to this filter to see if it will cause a hierarchy loop.
 	 *
 	 * @since 3.1.0
 	 *
 	// Check for duplicate slug
 	$duplicate = get_term_by( 'slug', $slug, $taxonomy );
 	if ( $duplicate && $duplicate->term_id != $term_id ) {
 		// If an empty slug was passed or the parent changed, reset the slug to something unique.
 		// Otherwise, bail.
-		if ( $empty_slug || ( $parent != $term['parent']) )
+		if ( $empty_slug || ( $parent != $term['parent']) ) {
 			$slug = wp_unique_term_slug($slug, (object) $args);
-		else
+		} else {
-			return new WP_Error('duplicate_term_slug', sprintf(__('The slug &#8220;%s&#8221; is already in use by another term'), $slug));
+			/* translators: 1: Taxonomy term slug */
-	}
+			return new WP_Error( 'duplicate_term_slug', sprintf( __( 'The slug &#8220;%s&#8221; is already in use by another term.' ), $slug ) );
+		}
-	$tt_id = $wpdb->get_var( $wpdb->prepare( "SELECT tt.term_taxonomy_id FROM $wpdb->term_taxonomy AS tt INNER JOIN $wpdb->terms AS t ON tt.term_id = t.term_id WHERE tt.taxonomy = %s AND t.term_id = %d", $taxonomy, $term_id) );
+	}
+	$tt_id = (int) $wpdb->get_var( $wpdb->prepare( "SELECT tt.term_taxonomy_id FROM $wpdb->term_taxonomy AS tt INNER JOIN $wpdb->terms AS t ON tt.term_id = t.term_id WHERE tt.taxonomy = %s AND t.term_id = %d", $taxonomy, $term_id) );
 	// Check whether this is a shared term that needs splitting.
 	$_term_id = _split_shared_term( $term_id, $tt_id );
 	if ( ! is_wp_error( $_term_id ) ) {
 		$term_id = $_term_id;
 	 *
 	 * @param int    $term_id  Term ID.
 	 * @param string $taxonomy Taxonomy slug.
 	 */
 	do_action( 'edit_terms', $term_id, $taxonomy );
-	$wpdb->update($wpdb->terms, compact( 'name', 'slug', 'term_group' ), compact( 'term_id' ) );
+	$data = compact( 'name', 'slug', 'term_group' );
+	/**
+	 * Filters term data before it is updated in the database.
+	 *
+	 * @since 4.7.0
+	 *
+	 * @param array  $data     Term data to be updated.
+	 * @param int    $term_id  Term ID.
+	 * @param string $taxonomy Taxonomy slug.
+	 * @param array  $args     Arguments passed to wp_update_term().
+	 */
+	$data = apply_filters( 'wp_update_term_data', $data, $term_id, $taxonomy, $args );
+	$wpdb->update( $wpdb->terms, $data, compact( 'term_id' ) );
 	if ( empty($slug) ) {
 		$slug = sanitize_title($name, $term_id);
 		$wpdb->update( $wpdb->terms, compact( 'slug' ), compact( 'term_id' ) );
 	}
 	 *
 	 * @param int    $tt_id    Term taxonomy ID.
 	 * @param string $taxonomy Taxonomy slug.
 	 */
 	do_action( 'edit_term_taxonomy', $tt_id, $taxonomy );
 	$wpdb->update( $wpdb->term_taxonomy, compact( 'term_id', 'taxonomy', 'description', 'parent' ), array( 'term_taxonomy_id' => $tt_id ) );
 	/**
 	 * Fires immediately after a term-taxonomy relationship is updated.
 	 *
 	 *
 	 * @param int    $tt_id    Term taxonomy ID.
 	 * @param string $taxonomy Taxonomy slug.
 	 */
 	do_action( 'edited_term_taxonomy', $tt_id, $taxonomy );
-	// Clean the relationship caches for all object types using this term
-	$objects = $wpdb->get_col( $wpdb->prepare( "SELECT object_id FROM $wpdb->term_relationships WHERE term_taxonomy_id = %d", $tt_id ) );
-	$tax_object = get_taxonomy( $taxonomy );
-	foreach ( $tax_object->object_type as $object_type ) {
-		clean_object_term_cache( $objects, $object_type );
-	}
 	/**
 	 * Fires after a term has been updated, but before the term cache has been cleaned.
 	 *
 	 * @since 2.3.0
 	 * @since 2.3.0
 	 *
 	 * @param int $term_id Term ID.
 	 * @param int $tt_id   Term taxonomy ID.
 	 */
-	do_action( "edit_$taxonomy", $term_id, $tt_id );
+	do_action( "edit_{$taxonomy}", $term_id, $tt_id );
 	/** This filter is documented in wp-includes/taxonomy.php */
 	$term_id = apply_filters( 'term_id_filter', $term_id, $tt_id );
 	clean_term_cache($term_id, $taxonomy);
 	 * @since 2.3.0
 	 *
 	 * @param int $term_id Term ID.
 	 * @param int $tt_id   Term taxonomy ID.
 	 */
-	do_action( "edited_$taxonomy", $term_id, $tt_id );
+	do_action( "edited_{$taxonomy}", $term_id, $tt_id );
 	return array('term_id' => $term_id, 'term_taxonomy_id' => $tt_id);
 }
 /**
 * Enable or disable term counting.
 *
 * @since 2.5.0
+*
+* @staticvar bool $_defer
 *
 * @param bool $defer Optional. Enable if true, disable if false.
 * @return bool Whether term counting is enabled or disabled.
 */
 function wp_defer_term_counting($defer=null) {
 * The default action is to count what the amount of terms have the relationship
 * of term ID. Once that is done, then update the database.
 *
 * @since 2.3.0
 *
-* @global wpdb $wpdb WordPress database abstraction object.
+* @staticvar array $_deferred
 *
-* @param int|array $terms The term_taxonomy_id of the terms
+* @param int|array $terms       The term_taxonomy_id of the terms.
-* @param string $taxonomy The context of the term.
+* @param string    $taxonomy    The context of the term.
+* @param bool      $do_deferred Whether to flush the deferred term counts too. Default false.
 * @return bool If no terms will return false, and if successful will return true.
 */
-function wp_update_term_count( $terms, $taxonomy, $do_deferred=false ) {
+function wp_update_term_count( $terms, $taxonomy, $do_deferred = false ) {
 	static $_deferred = array();
 	if ( $do_deferred ) {
 		foreach ( (array) array_keys($_deferred) as $tax ) {
 			wp_update_term_count_now( $_deferred[$tax], $tax );
 /**
 * Perform term count update immediately.
 *
 * @since 2.5.0
 *
-* @param array $terms The term_taxonomy_id of terms to update.
+* @param array  $terms    The term_taxonomy_id of terms to update.
 * @param string $taxonomy The context of the term.
-* @return bool Always true when complete.
+* @return true Always true when complete.
 */
 function wp_update_term_count_now( $terms, $taxonomy ) {
 	$terms = array_map('intval', $terms);
 	$taxonomy = get_taxonomy($taxonomy);
 //
 /**
 * Removes the taxonomy relationship to terms from the cache.
 *
-* Will remove the entire taxonomy relationship containing term $object_id. The
+* Will remove the entire taxonomy relationship containing term `$object_id`. The
-* term IDs have to exist within the taxonomy $object_type for the deletion to
+* term IDs have to exist within the taxonomy `$object_type` for the deletion to
 * take place.
 *
 * @since 2.3.0
 *
-* @see get_object_taxonomies() for more on $object_type
+* @global bool $_wp_suspend_cache_invalidation
 *
-* @param int|array $object_ids Single or list of term object ID(s)
+* @see get_object_taxonomies() for more on $object_type.
-* @param array|string $object_type The taxonomy object type
+*
+* @param int|array    $object_ids  Single or list of term object ID(s).
+* @param array|string $object_type The taxonomy object type.
 */
 function clean_object_term_cache($object_ids, $object_type) {
+	global $_wp_suspend_cache_invalidation;
+	if ( ! empty( $_wp_suspend_cache_invalidation ) ) {
+		return;
+	}
 	if ( !is_array($object_ids) )
 		$object_ids = array($object_ids);
 	$taxonomies = get_object_taxonomies( $object_type );
 	 * Fires after the object term cache has been cleaned.
 	 *
 	 * @since 2.5.0
 	 *
 	 * @param array  $object_ids An array of object IDs.
-	 * @param string $objet_type Object type.
+	 * @param string $object_type Object type.
 	 */
 	do_action( 'clean_object_term_cache', $object_ids, $object_type );
 }
 /**
 * Will remove all of the term ids from the cache.
 *
 * @since 2.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
-*
+* @global bool $_wp_suspend_cache_invalidation
-* @param int|array $ids Single or list of Term IDs
+*
-* @param string $taxonomy Can be empty and will assume tt_ids, else will use for context.
+* @param int|array $ids            Single or list of Term IDs.
-* @param bool $clean_taxonomy Whether to clean taxonomy wide caches (true), or just individual term object caches (false). Default is true.
+* @param string    $taxonomy       Optional. Can be empty and will assume `tt_ids`, else will use for context.
+*                                  Default empty.
+* @param bool      $clean_taxonomy Optional. Whether to clean taxonomy wide caches (true), or just individual
+*                                  term object caches (false). Default true.
 */
 function clean_term_cache($ids, $taxonomy = '', $clean_taxonomy = true) {
-	global $wpdb;
+	global $wpdb, $_wp_suspend_cache_invalidation;
+	if ( ! empty( $_wp_suspend_cache_invalidation ) ) {
+		return;
+	}
 	if ( !is_array($ids) )
 		$ids = array($ids);
 	$taxonomies = array();
 		$terms = $wpdb->get_results("SELECT term_id, taxonomy FROM $wpdb->term_taxonomy WHERE term_taxonomy_id IN ($tt_ids)");
 		$ids = array();
 		foreach ( (array) $terms as $term ) {
 			$taxonomies[] = $term->taxonomy;
 			$ids[] = $term->term_id;
-			wp_cache_delete($term->term_id, $term->taxonomy);
+			wp_cache_delete( $term->term_id, 'terms' );
 		}
 		$taxonomies = array_unique($taxonomies);
 	} else {
 		$taxonomies = array($taxonomy);
 		foreach ( $taxonomies as $taxonomy ) {
 			foreach ( $ids as $id ) {
-				wp_cache_delete($id, $taxonomy);
+				wp_cache_delete( $id, 'terms' );
 			}
 		}
 	}
 	foreach ( $taxonomies as $taxonomy ) {
 		if ( $clean_taxonomy ) {
-			wp_cache_delete('all_ids', $taxonomy);
+			clean_taxonomy_cache( $taxonomy );
-			wp_cache_delete('get', $taxonomy);
-			delete_option("{$taxonomy}_children");
-			// Regenerate {$taxonomy}_children
-			_get_term_hierarchy($taxonomy);
 		}
 		/**
 		 * Fires once after each taxonomy's term cache has been cleaned.
 		 *
 		 * @since 2.5.0
+		 * @since 4.5.0 Added the `$clean_taxonomy` parameter.
 		 *
-		 * @param array  $ids      An array of term IDs.
+		 * @param array  $ids            An array of term IDs.
-		 * @param string $taxonomy Taxonomy slug.
+		 * @param string $taxonomy       Taxonomy slug.
+		 * @param bool   $clean_taxonomy Whether or not to clean taxonomy-wide caches
 		 */
-		do_action( 'clean_term_cache', $ids, $taxonomy );
+		do_action( 'clean_term_cache', $ids, $taxonomy, $clean_taxonomy );
 	}
 	wp_cache_set( 'last_changed', microtime(), 'terms' );
 }
 /**
+* Clean the caches for a taxonomy.
+*
+* @since 4.9.0
+*
+* @param string $taxonomy Taxonomy slug.
+*/
+function clean_taxonomy_cache( $taxonomy ) {
+	wp_cache_delete( 'all_ids', $taxonomy );
+	wp_cache_delete( 'get', $taxonomy );
+	// Regenerate cached hierarchy.
+	delete_option( "{$taxonomy}_children" );
+	_get_term_hierarchy( $taxonomy );
+	/**
+	 * Fires after a taxonomy's caches have been cleaned.
+	 *
+	 * @since 4.9.0
+	 *
+	 * @param string $taxonomy Taxonomy slug.
+	 */
+	do_action( 'clean_taxonomy_cache', $taxonomy );
+}
+/**
 * Retrieves the taxonomy relationship to the term object id.
 *
+* Upstream functions (like get_the_terms() and is_object_in_term()) are
+* responsible for populating the object-term relationship cache. The current
+* function only fetches relationship data that is already in the cache.
+*
 * @since 2.3.0
-*
+* @since 4.7.0 Returns a WP_Error object if get_term() returns an error for
-* @param int    $id       Term object ID
+*              any of the matched terms.
-* @param string $taxonomy Taxonomy Name
+*
-* @return bool|array Empty array if $terms found, but not $taxonomy. False if nothing is in cache for $taxonomy and $id.
+* @param int    $id       Term object ID.
-*/
+* @param string $taxonomy Taxonomy name.
-function get_object_term_cache($id, $taxonomy) {
+* @return bool|array|WP_Error Array of `WP_Term` objects, if cached.
-	$cache = wp_cache_get($id, "{$taxonomy}_relationships");
+*                             False if cache is empty for `$taxonomy` and `$id`.
-	return $cache;
+*                             WP_Error if get_term() returns an error object for any term.
+*/
+function get_object_term_cache( $id, $taxonomy ) {
+	$_term_ids = wp_cache_get( $id, "{$taxonomy}_relationships" );
+	// We leave the priming of relationship caches to upstream functions.
+	if ( false === $_term_ids ) {
+		return false;
+	}
+	// Backward compatibility for if a plugin is putting objects into the cache, rather than IDs.
+	$term_ids = array();
+	foreach ( $_term_ids as $term_id ) {
+		if ( is_numeric( $term_id ) ) {
+			$term_ids[] = intval( $term_id );
+		} elseif ( isset( $term_id->term_id ) ) {
+			$term_ids[] = intval( $term_id->term_id );
+		}
+	}
+	// Fill the term objects.
+	_prime_term_caches( $term_ids );
+	$terms = array();
+	foreach ( $term_ids as $term_id ) {
+		$term = get_term( $term_id, $taxonomy );
+		if ( is_wp_error( $term ) ) {
+			return $term;
+		}
+		$terms[] = $term;
+	}
+	return $terms;
 }
 /**
 * Updates the cache for the given term object ID(s).
 *
 *
 * Caches will only be updated for terms not already cached.
 *
 * @since 2.3.0
 *
-* @param string|array $object_ids  Comma-separated list or array of term object IDs..
+* @param string|array $object_ids  Comma-separated list or array of term object IDs.
 * @param array|string $object_type The taxonomy object type.
-* @return null|false Null if `$object_ids` is empty, false if all of the terms in
+* @return void|false False if all of the terms in `$object_ids` are already cached.
-*                    `$object_ids` are already cached.
 */
 function update_object_term_cache($object_ids, $object_type) {
 	if ( empty($object_ids) )
 		return;
 	}
 	if ( empty( $ids ) )
 		return false;
-	$terms = wp_get_object_terms($ids, $taxonomies, array('fields' => 'all_with_object_id'));
+	$terms = wp_get_object_terms( $ids, $taxonomies, array(
+		'fields' => 'all_with_object_id',
+		'orderby' => 'name',
+		'update_term_meta_cache' => false,
+	) );
 	$object_terms = array();
-	foreach ( (array) $terms as $term )
+	foreach ( (array) $terms as $term ) {
-		$object_terms[$term->object_id][$term->taxonomy][] = $term;
+		$object_terms[ $term->object_id ][ $term->taxonomy ][] = $term->term_id;
+	}
 	foreach ( $ids as $id ) {
 		foreach ( $taxonomies as $taxonomy ) {
 			if ( ! isset($object_terms[$id][$taxonomy]) ) {
 				if ( !isset($object_terms[$id]) )
 /**
 * Updates Terms to Taxonomy in cache.
 *
 * @since 2.3.0
 *
-* @param array $terms List of Term objects to change
+* @param array  $terms    List of term objects to change.
-* @param string $taxonomy Optional. Update Term to this taxonomy in cache
+* @param string $taxonomy Optional. Update Term to this taxonomy in cache. Default empty.
 */
-function update_term_cache($terms, $taxonomy = '') {
+function update_term_cache( $terms, $taxonomy = '' ) {
 	foreach ( (array) $terms as $term ) {
-		$term_taxonomy = $taxonomy;
+		// Create a copy in case the array was passed by reference.
-		if ( empty($term_taxonomy) )
+		$_term = clone $term;
-			$term_taxonomy = $term->taxonomy;
+		// Object ID should not be cached.
-		wp_cache_add( $term->term_id, $term, $term_taxonomy );
+		unset( $_term->object_id );
+		wp_cache_add( $term->term_id, $_term, 'terms' );
 	}
 }
 //
 // Private
 //
 /**
 * Retrieves children of taxonomy as Term IDs.
 *
-* @access private
+* @ignore
 * @since 2.3.0
 *
-* @param string $taxonomy Taxonomy Name
+* @param string $taxonomy Taxonomy name.
 * @return array Empty if $taxonomy isn't hierarchical or returns children as Term IDs.
 */
-function _get_term_hierarchy($taxonomy) {
+function _get_term_hierarchy( $taxonomy ) {
 	if ( !is_taxonomy_hierarchical($taxonomy) )
 		return array();
 	$children = get_option("{$taxonomy}_children");
 	if ( is_array($children) )
 }
 /**
 * Get the subset of $terms that are descendants of $term_id.
 *
-* If $terms is an array of objects, then _get_term_children returns an array of objects.
+* If `$terms` is an array of objects, then _get_term_children() returns an array of objects.
-* If $terms is an array of IDs, then _get_term_children returns an array of IDs.
+* If `$terms` is an array of IDs, then _get_term_children() returns an array of IDs.
 *
 * @access private
 * @since 2.3.0
 *
-* @param int $term_id The ancestor term: all returned terms should be descendants of $term_id.
+* @param int    $term_id   The ancestor term: all returned terms should be descendants of `$term_id`.
 * @param array  $terms     The set of terms - either an array of term objects or term IDs - from which those that
 *                          are descendants of $term_id will be chosen.
 * @param string $taxonomy  The taxonomy which determines the hierarchy of the terms.
-* @param array  $ancestors Term ancestors that have already been identified. Passed by reference, to keep track of
+* @param array  $ancestors Optional. Term ancestors that have already been identified. Passed by reference, to keep
-*                          found terms when recursing the hierarchy. The array of located ancestors is used to prevent
+*                          track of found terms when recursing the hierarchy. The array of located ancestors is used
-*                          infinite recursion loops. For performance, term_ids are used as array keys, with 1 as value.
+*                          to prevent infinite recursion loops. For performance, `term_ids` are used as array keys,
-* @return array The subset of $terms that are descendants of $term_id.
+*                          with 1 as value. Default empty array.
+* @return array|WP_Error The subset of $terms that are descendants of $term_id.
 */
 function _get_term_children( $term_id, $terms, $taxonomy, &$ancestors = array() ) {
 	$empty_array = array();
 	if ( empty($terms) )
 		return $empty_array;
 * @access private
 * @since 2.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
-* @param array $terms List of Term IDs
+* @param array  $terms    List of term objects (passed by reference).
-* @param string $taxonomy Term Context
+* @param string $taxonomy Term context.
-* @return null Will break from function if conditions are not met.
+*/
-*/
+function _pad_term_counts( &$terms, $taxonomy ) {
-function _pad_term_counts(&$terms, $taxonomy) {
 	global $wpdb;
 	// This function only works for hierarchical taxonomies like post categories.
 	if ( !is_taxonomy_hierarchical( $taxonomy ) )
 		return;
 	foreach ( (array) $terms as $key => $term ) {
 		$terms_by_id[$term->term_id] = & $terms[$key];
 		$term_ids[$term->term_taxonomy_id] = $term->term_id;
 	}
-	// Get the object and term ids and stick them in a lookup table
+	// Get the object and term ids and stick them in a lookup table.
 	$tax_obj = get_taxonomy($taxonomy);
 	$object_types = esc_sql($tax_obj->object_type);
 	$results = $wpdb->get_results("SELECT object_id, term_taxonomy_id FROM $wpdb->term_relationships INNER JOIN $wpdb->posts ON object_id = ID WHERE term_taxonomy_id IN (" . implode(',', array_keys($term_ids)) . ") AND post_type IN ('" . implode("', '", $object_types) . "') AND post_status = 'publish'");
 	foreach ( $results as $row ) {
 		$id = $term_ids[$row->term_taxonomy_id];
 		$term_items[$id][$row->object_id] = isset($term_items[$id][$row->object_id]) ? ++$term_items[$id][$row->object_id] : 1;
 	}
-	// Touch every ancestor's lookup row for each post in each term
+	// Touch every ancestor's lookup row for each post in each term.
 	foreach ( $term_ids as $term_id ) {
 		$child = $term_id;
 		$ancestors = array();
 		while ( !empty( $terms_by_id[$child] ) && $parent = $terms_by_id[$child]->parent ) {
 			$ancestors[] = $child;
 				break;
 			}
 		}
 	}
-	// Transfer the touched cells
+	// Transfer the touched cells.
 	foreach ( (array) $term_items as $id => $items )
 		if ( isset($terms_by_id[$id]) )
 			$terms_by_id[$id]->count = count($items);
 }
+/**
+* Adds any terms from the given IDs to the cache that do not already exist in cache.
+*
+* @since 4.6.0
+* @access private
+*
+* @global wpdb $wpdb WordPress database abstraction object.
+*
+* @param array $term_ids          Array of term IDs.
+* @param bool  $update_meta_cache Optional. Whether to update the meta cache. Default true.
+*/
+function _prime_term_caches( $term_ids, $update_meta_cache = true ) {
+	global $wpdb;
+	$non_cached_ids = _get_non_cached_ids( $term_ids, 'terms' );
+	if ( ! empty( $non_cached_ids ) ) {
+		$fresh_terms = $wpdb->get_results( sprintf( "SELECT t.*, tt.* FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id WHERE t.term_id IN (%s)", join( ",", array_map( 'intval', $non_cached_ids ) ) ) );
+		update_term_cache( $fresh_terms, $update_meta_cache );
+		if ( $update_meta_cache ) {
+			update_termmeta_cache( $non_cached_ids );
+		}
+	}
+}
 //
 // Default callbacks
 //
 /**
 * @access private
 * @since 2.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
-* @param array $terms List of Term taxonomy IDs
+* @param array  $terms    List of Term taxonomy IDs.
-* @param object $taxonomy Current taxonomy object of terms
+* @param object $taxonomy Current taxonomy object of terms.
 */
 function _update_post_term_count( $terms, $taxonomy ) {
 	global $wpdb;
 	$object_types = (array) $taxonomy->object_type;
 		$object_types = esc_sql( array_filter( $object_types, 'post_type_exists' ) );
 	foreach ( (array) $terms as $term ) {
 		$count = 0;
-		// Attachments can be 'inherit' status, we need to base count off the parent's status if so
+		// Attachments can be 'inherit' status, we need to base count off the parent's status if so.
 		if ( $check_attachments )
 			$count += (int) $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM $wpdb->term_relationships, $wpdb->posts p1 WHERE p1.ID = $wpdb->term_relationships.object_id AND ( post_status = 'publish' OR ( post_status = 'inherit' AND post_parent > 0 AND ( SELECT post_status FROM $wpdb->posts WHERE ID = p1.post_parent ) = 'publish' ) ) AND post_type = 'attachment' AND term_taxonomy_id = %d", $term ) );
 		if ( $object_types )
 			$count += (int) $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM $wpdb->term_relationships, $wpdb->posts WHERE $wpdb->posts.ID = $wpdb->term_relationships.object_id AND post_status = 'publish' AND post_type IN ('" . implode("', '", $object_types ) . "') AND term_taxonomy_id = %d", $term ) );
 }
 /**
 * Will update term count based on number of objects.
 *
-* Default callback for the link_category taxonomy.
+* Default callback for the 'link_category' taxonomy.
 *
 * @since 3.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
-* @param array $terms List of Term taxonomy IDs
+* @param array  $terms    List of term taxonomy IDs.
-* @param object $taxonomy Current taxonomy object of terms
+* @param object $taxonomy Current taxonomy object of terms.
 */
 function _update_generic_term_count( $terms, $taxonomy ) {
 	global $wpdb;
 	foreach ( (array) $terms as $term ) {
 		do_action( 'edited_term_taxonomy', $term, $taxonomy->name );
 	}
 }
 /**
-* Create a new term for a term_taxonomy item that currently shares its term with another term_taxonomy.
+* Create a new term for a term_taxonomy item that currently shares its term
+* with another term_taxonomy.
 *
 * @ignore
 * @since 4.2.0
-*
+* @since 4.3.0 Introduced `$record` parameter. Also, `$term_id` and
-* @param int  $term_id          ID of the shared term.
+*              `$term_taxonomy_id` can now accept objects.
-* @param int  $term_taxonomy_id ID of the term_taxonomy item to receive a new term.
+*
+* @global wpdb $wpdb WordPress database abstraction object.
+*
+* @param int|object $term_id          ID of the shared term, or the shared term object.
+* @param int|object $term_taxonomy_id ID of the term_taxonomy item to receive a new term, or the term_taxonomy object
+*                                     (corresponding to a row from the term_taxonomy table).
+* @param bool       $record           Whether to record data about the split term in the options table. The recording
+*                                     process has the potential to be resource-intensive, so during batch operations
+*                                     it can be beneficial to skip inline recording and do it just once, after the
+*                                     batch is processed. Only set this to `false` if you know what you are doing.
+*                                     Default: true.
 * @return int|WP_Error When the current term does not need to be split (or cannot be split on the current
 *                      database schema), `$term_id` is returned. When the term is successfully split, the
 *                      new term_id is returned. A WP_Error is returned for miscellaneous errors.
 */
-function _split_shared_term( $term_id, $term_taxonomy_id ) {
+function _split_shared_term( $term_id, $term_taxonomy_id, $record = true ) {
 	global $wpdb;
-	// Don't try to split terms if database schema does not support shared slugs.
+	if ( is_object( $term_id ) ) {
-	$current_db_version = get_option( 'db_version' );
+		$shared_term = $term_id;
-	if ( $current_db_version < 30133 ) {
+		$term_id = intval( $shared_term->term_id );
-		return $term_id;
+	}
+	if ( is_object( $term_taxonomy_id ) ) {
+		$term_taxonomy = $term_taxonomy_id;
+		$term_taxonomy_id = intval( $term_taxonomy->term_taxonomy_id );
 	}
 	// If there are no shared term_taxonomy rows, there's nothing to do here.
 	$shared_tt_count = $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM $wpdb->term_taxonomy tt WHERE tt.term_id = %d AND tt.term_taxonomy_id != %d", $term_id, $term_taxonomy_id ) );
 	if ( ! $shared_tt_count ) {
 		return $term_id;
 	}
+	/*
+	 * Verify that the term_taxonomy_id passed to the function is actually associated with the term_id.
+	 * If there's a mismatch, it may mean that the term is already split. Return the actual term_id from the db.
+	 */
+	$check_term_id = $wpdb->get_var( $wpdb->prepare( "SELECT term_id FROM $wpdb->term_taxonomy WHERE term_taxonomy_id = %d", $term_taxonomy_id ) );
+	if ( $check_term_id != $term_id ) {
+		return $check_term_id;
+	}
 	// Pull up data about the currently shared slug, which we'll use to populate the new one.
-	$shared_term = $wpdb->get_row( $wpdb->prepare( "SELECT t.* FROM $wpdb->terms t WHERE t.term_id = %d", $term_id ) );
+	if ( empty( $shared_term ) ) {
+		$shared_term = $wpdb->get_row( $wpdb->prepare( "SELECT t.* FROM $wpdb->terms t WHERE t.term_id = %d", $term_id ) );
+	}
 	$new_term_data = array(
 		'name' => $shared_term->name,
 		'slug' => $shared_term->slug,
 		'term_group' => $shared_term->term_group,
 		array( 'term_id' => $new_term_id ),
 		array( 'term_taxonomy_id' => $term_taxonomy_id )
 	);
 	// Reassign child terms to the new parent.
-	$term_taxonomy = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM $wpdb->term_taxonomy WHERE term_taxonomy_id = %d", $term_taxonomy_id ) );
+	if ( empty( $term_taxonomy ) ) {
-	$children_tt_ids = $wpdb->get_col( $wpdb->prepare( "SELECT term_taxonomy_id FROM $wpdb->term_taxonomy WHERE taxonomy = %s AND parent = %d", $term_taxonomy->taxonomy, $term_id ) );
+		$term_taxonomy = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM $wpdb->term_taxonomy WHERE term_taxonomy_id = %d", $term_taxonomy_id ) );
+	}
+	$children_tt_ids = $wpdb->get_col( $wpdb->prepare( "SELECT term_taxonomy_id FROM $wpdb->term_taxonomy WHERE parent = %d AND taxonomy = %s", $term_id, $term_taxonomy->taxonomy ) );
 	if ( ! empty( $children_tt_ids ) ) {
 		foreach ( $children_tt_ids as $child_tt_id ) {
 			$wpdb->update( $wpdb->term_taxonomy,
 				array( 'parent' => $new_term_id ),
 				array( 'term_taxonomy_id' => $child_tt_id )
 			);
-			clean_term_cache( $term_id, $term_taxonomy->taxonomy );
+			clean_term_cache( (int) $child_tt_id, '', false );
 		}
 	} else {
 		// If the term has no children, we must force its taxonomy cache to be rebuilt separately.
-		clean_term_cache( $new_term_id, $term_taxonomy->taxonomy );
+		clean_term_cache( $new_term_id, $term_taxonomy->taxonomy, false );
 	}
+	clean_term_cache( $term_id, $term_taxonomy->taxonomy, false );
+	/*
+	 * Taxonomy cache clearing is delayed to avoid race conditions that may occur when
+	 * regenerating the taxonomy's hierarchy tree.
+	 */
+	$taxonomies_to_clean = array( $term_taxonomy->taxonomy );
 	// Clean the cache for term taxonomies formerly shared with the current term.
-	$shared_term_taxonomies = $wpdb->get_row( $wpdb->prepare( "SELECT taxonomy FROM $wpdb->term_taxonomy WHERE term_id = %d", $term_id ) );
+	$shared_term_taxonomies = $wpdb->get_col( $wpdb->prepare( "SELECT taxonomy FROM $wpdb->term_taxonomy WHERE term_id = %d", $term_id ) );
-	if ( $shared_term_taxonomies ) {
+	$taxonomies_to_clean = array_merge( $taxonomies_to_clean, $shared_term_taxonomies );
-		foreach ( $shared_term_taxonomies as $shared_term_taxonomy ) {
-			clean_term_cache( $term_id, $shared_term_taxonomy );
+	foreach ( $taxonomies_to_clean as $taxonomy_to_clean ) {
-		}
+		clean_taxonomy_cache( $taxonomy_to_clean );
 	}
-	// Keep a record of term_ids that have been split, keyed by old term_id. See {@see wp_get_split_term()}.
+	// Keep a record of term_ids that have been split, keyed by old term_id. See wp_get_split_term().
-	$split_term_data = get_option( '_split_terms', array() );
+	if ( $record ) {
-	if ( ! isset( $split_term_data[ $term_id ] ) ) {
+		$split_term_data = get_option( '_split_terms', array() );
-		$split_term_data[ $term_id ] = array();
+		if ( ! isset( $split_term_data[ $term_id ] ) ) {
-	}
+			$split_term_data[ $term_id ] = array();
+		}
-	$split_term_data[ $term_id ][ $term_taxonomy->taxonomy ] = $new_term_id;
+		$split_term_data[ $term_id ][ $term_taxonomy->taxonomy ] = $new_term_id;
-	update_option( '_split_terms', $split_term_data );
+		update_option( '_split_terms', $split_term_data );
+	}
+	// If we've just split the final shared term, set the "finished" flag.
+	$shared_terms_exist = $wpdb->get_results(
+		"SELECT tt.term_id, t.*, count(*) as term_tt_count FROM {$wpdb->term_taxonomy} tt
+		 LEFT JOIN {$wpdb->terms} t ON t.term_id = tt.term_id
+		 GROUP BY t.term_id
+		 HAVING term_tt_count > 1
+		 LIMIT 1"
+	);
+	if ( ! $shared_terms_exist ) {
+		update_option( 'finished_splitting_shared_terms', true );
+	}
 	/**
 	 * Fires after a previously shared taxonomy term is split into two separate terms.
 	 *
 	 * @since 4.2.0
 	return $new_term_id;
 }
 /**
+* Splits a batch of shared taxonomy terms.
+*
+* @since 4.3.0
+*
+* @global wpdb $wpdb WordPress database abstraction object.
+*/
+function _wp_batch_split_terms() {
+	global $wpdb;
+	$lock_name = 'term_split.lock';
+	// Try to lock.
+	$lock_result = $wpdb->query( $wpdb->prepare( "INSERT IGNORE INTO `$wpdb->options` ( `option_name`, `option_value`, `autoload` ) VALUES (%s, %s, 'no') /* LOCK */", $lock_name, time() ) );
+	if ( ! $lock_result ) {
+		$lock_result = get_option( $lock_name );
+		// Bail if we were unable to create a lock, or if the existing lock is still valid.
+		if ( ! $lock_result || ( $lock_result > ( time() - HOUR_IN_SECONDS ) ) ) {
+			wp_schedule_single_event( time() + ( 5 * MINUTE_IN_SECONDS ), 'wp_split_shared_term_batch' );
+			return;
+		}
+	}
+	// Update the lock, as by this point we've definitely got a lock, just need to fire the actions.
+	update_option( $lock_name, time() );
+	// Get a list of shared terms (those with more than one associated row in term_taxonomy).
+	$shared_terms = $wpdb->get_results(
+		"SELECT tt.term_id, t.*, count(*) as term_tt_count FROM {$wpdb->term_taxonomy} tt
+		 LEFT JOIN {$wpdb->terms} t ON t.term_id = tt.term_id
+		 GROUP BY t.term_id
+		 HAVING term_tt_count > 1
+		 LIMIT 10"
+	);
+	// No more terms, we're done here.
+	if ( ! $shared_terms ) {
+		update_option( 'finished_splitting_shared_terms', true );
+		delete_option( $lock_name );
+		return;
+	}
+	// Shared terms found? We'll need to run this script again.
+	wp_schedule_single_event( time() + ( 2 * MINUTE_IN_SECONDS ), 'wp_split_shared_term_batch' );
+	// Rekey shared term array for faster lookups.
+	$_shared_terms = array();
+	foreach ( $shared_terms as $shared_term ) {
+		$term_id = intval( $shared_term->term_id );
+		$_shared_terms[ $term_id ] = $shared_term;
+	}
+	$shared_terms = $_shared_terms;
+	// Get term taxonomy data for all shared terms.
+	$shared_term_ids = implode( ',', array_keys( $shared_terms ) );
+	$shared_tts = $wpdb->get_results( "SELECT * FROM {$wpdb->term_taxonomy} WHERE `term_id` IN ({$shared_term_ids})" );
+	// Split term data recording is slow, so we do it just once, outside the loop.
+	$split_term_data = get_option( '_split_terms', array() );
+	$skipped_first_term = $taxonomies = array();
+	foreach ( $shared_tts as $shared_tt ) {
+		$term_id = intval( $shared_tt->term_id );
+		// Don't split the first tt belonging to a given term_id.
+		if ( ! isset( $skipped_first_term[ $term_id ] ) ) {
+			$skipped_first_term[ $term_id ] = 1;
+			continue;
+		}
+		if ( ! isset( $split_term_data[ $term_id ] ) ) {
+			$split_term_data[ $term_id ] = array();
+		}
+		// Keep track of taxonomies whose hierarchies need flushing.
+		if ( ! isset( $taxonomies[ $shared_tt->taxonomy ] ) ) {
+			$taxonomies[ $shared_tt->taxonomy ] = 1;
+		}
+		// Split the term.
+		$split_term_data[ $term_id ][ $shared_tt->taxonomy ] = _split_shared_term( $shared_terms[ $term_id ], $shared_tt, false );
+	}
+	// Rebuild the cached hierarchy for each affected taxonomy.
+	foreach ( array_keys( $taxonomies ) as $tax ) {
+		delete_option( "{$tax}_children" );
+		_get_term_hierarchy( $tax );
+	}
+	update_option( '_split_terms', $split_term_data );
+	delete_option( $lock_name );
+}
+/**
+* In order to avoid the _wp_batch_split_terms() job being accidentally removed,
+* check that it's still scheduled while we haven't finished splitting terms.
+*
+* @ignore
+* @since 4.3.0
+*/
+function _wp_check_for_scheduled_split_terms() {
+	if ( ! get_option( 'finished_splitting_shared_terms' ) && ! wp_next_scheduled( 'wp_split_shared_term_batch' ) ) {
+		wp_schedule_single_event( time() + MINUTE_IN_SECONDS, 'wp_split_shared_term_batch' );
+	}
+}
+/**
 * Check default categories when a term gets split to see if any of them need to be updated.
 *
 * @ignore
 * @since 4.2.0
 *
 /**
 * Check menu items when a term gets split to see if any of them need to be updated.
 *
 * @ignore
 * @since 4.2.0
+*
+* @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param int    $term_id          ID of the formerly shared term.
 * @param int    $new_term_id      ID of the new term created for the $term_taxonomy_id.
 * @param int    $term_taxonomy_id ID for the term_taxonomy row affected by the split.
 * @param string $taxonomy         Taxonomy for the split term.
 		"SELECT m1.post_id
 		FROM {$wpdb->postmeta} AS m1
 			INNER JOIN {$wpdb->postmeta} AS m2 ON ( m2.post_id = m1.post_id )
 			INNER JOIN {$wpdb->postmeta} AS m3 ON ( m3.post_id = m1.post_id )
 		WHERE ( m1.meta_key = '_menu_item_type' AND m1.meta_value = 'taxonomy' )
-			AND ( m2.meta_key = '_menu_item_object' AND m2.meta_value = '%s' )
+			AND ( m2.meta_key = '_menu_item_object' AND m2.meta_value = %s )
 			AND ( m3.meta_key = '_menu_item_object_id' AND m3.meta_value = %d )",
 		$taxonomy,
 		$term_id
 	) );
 		}
 	}
 }
 /**
+* If the term being split is a nav_menu, change associations.
+*
+* @ignore
+* @since 4.3.0
+*
+* @param int    $term_id          ID of the formerly shared term.
+* @param int    $new_term_id      ID of the new term created for the $term_taxonomy_id.
+* @param int    $term_taxonomy_id ID for the term_taxonomy row affected by the split.
+* @param string $taxonomy         Taxonomy for the split term.
+*/
+function _wp_check_split_nav_menu_terms( $term_id, $new_term_id, $term_taxonomy_id, $taxonomy ) {
+	if ( 'nav_menu' !== $taxonomy ) {
+		return;
+	}
+	// Update menu locations.
+	$locations = get_nav_menu_locations();
+	foreach ( $locations as $location => $menu_id ) {
+		if ( $term_id == $menu_id ) {
+			$locations[ $location ] = $new_term_id;
+		}
+	}
+	set_theme_mod( 'nav_menu_locations', $locations );
+}
+/**
 * Get data about terms that previously shared a single term_id, but have since been split.
 *
 * @since 4.2.0
 *
 * @param int $old_term_id Term ID. This is the old, pre-split term ID.
 *
 * @since 4.2.0
 *
 * @param int    $old_term_id Term ID. This is the old, pre-split term ID.
 * @param string $taxonomy    Taxonomy that the term belongs to.
-* @return bool|int If a previously split term is found corresponding to the old term_id and taxonomy,
+* @return int|false If a previously split term is found corresponding to the old term_id and taxonomy,
-*                  the new term_id will be returned. If no previously split term is found matching
+*                   the new term_id will be returned. If no previously split term is found matching
-*                  the parameters, returns false.
+*                   the parameters, returns false.
 */
 function wp_get_split_term( $old_term_id, $taxonomy ) {
 	$split_terms = wp_get_split_terms( $old_term_id );
 	$term_id = false;
 	return $term_id;
 }
 /**
+* Determine whether a term is shared between multiple taxonomies.
+*
+* Shared taxonomy terms began to be split in 4.3, but failed cron tasks or
+* other delays in upgrade routines may cause shared terms to remain.
+*
+* @since 4.4.0
+*
+* @param int $term_id Term ID.
+* @return bool Returns false if a term is not shared between multiple taxonomies or
+*              if splittng shared taxonomy terms is finished.
+*/
+function wp_term_is_shared( $term_id ) {
+	global $wpdb;
+	if ( get_option( 'finished_splitting_shared_terms' ) ) {
+		return false;
+	}
+	$tt_count = $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM $wpdb->term_taxonomy WHERE term_id = %d", $term_id ) );
+	return $tt_count > 1;
+}
+/**
 * Generate a permalink for a taxonomy term archive.
 *
 * @since 2.5.0
+*
+* @global WP_Rewrite $wp_rewrite
 *
 * @param object|int|string $term     The term object, ID, or slug whose link will be retrieved.
 * @param string            $taxonomy Optional. Taxonomy. Default empty.
 * @return string|WP_Error HTML link to taxonomy term archive on success, WP_Error if term does not exist.
 */
-function get_term_link( $term, $taxonomy = '') {
+function get_term_link( $term, $taxonomy = '' ) {
 	global $wp_rewrite;
 	if ( !is_object($term) ) {
-		if ( is_int($term) ) {
+		if ( is_int( $term ) ) {
-			$term = get_term($term, $taxonomy);
+			$term = get_term( $term, $taxonomy );
 		} else {
-			$term = get_term_by('slug', $term, $taxonomy);
+			$term = get_term_by( 'slug', $term, $taxonomy );
 		}
 	}
 	if ( !is_object($term) )
-		$term = new WP_Error('invalid_term', __('Empty Term'));
+		$term = new WP_Error( 'invalid_term', __( 'Empty Term.' ) );
 	if ( is_wp_error( $term ) )
 		return $term;
 	$taxonomy = $term->taxonomy;
 	$termlink = $wp_rewrite->get_extra_permastruct($taxonomy);
+	/**
+	 * Filters the permalink structure for a terms before token replacement occurs.
+	 *
+	 * @since 4.9.0
+	 *
+	 * @param string  $termlink The permalink structure for the term's taxonomy.
+	 * @param WP_Term $term     The term object.
+	 */
+	$termlink = apply_filters( 'pre_term_link', $termlink, $term );
 	$slug = $term->slug;
 	$t = get_taxonomy($taxonomy);
 	if ( empty($termlink) ) {
 	}
 	// Back Compat filters.
 	if ( 'post_tag' == $taxonomy ) {
 		/**
-		 * Filter the tag link.
+		 * Filters the tag link.
 		 *
 		 * @since 2.3.0
 		 * @deprecated 2.5.0 Use 'term_link' instead.
 		 *
 		 * @param string $termlink Tag link URL.
 		 */
 		$termlink = apply_filters( 'tag_link', $termlink, $term->term_id );
 	} elseif ( 'category' == $taxonomy ) {
 		/**
-		 * Filter the category link.
+		 * Filters the category link.
 		 *
 		 * @since 1.5.0
 		 * @deprecated 2.5.0 Use 'term_link' instead.
 		 *
 		 * @param string $termlink Category link URL.
 		 */
 		$termlink = apply_filters( 'category_link', $termlink, $term->term_id );
 	}
 	/**
-	 * Filter the term link.
+	 * Filters the term link.
 	 *
 	 * @since 2.5.0
 	 *
 	 * @param string $termlink Term link URL.
 	 * @param object $term     Term object.
 * display the taxonomies for a specific post.
 *
 * @since 2.5.0
 *
 * @param array $args {
-*     Arguments about which post to use and how to format the output. Shares all of the arguments supported by
+*     Arguments about which post to use and how to format the output. Shares all of the arguments
-*     {@link get_the_taxonomies()}, in addition to the following.
+*     supported by get_the_taxonomies(), in addition to the following.
 *
 *     @type  int|WP_Post $post   Post ID or object to get taxonomies of. Default current post.
 *     @type  string      $before Displays before the taxonomies. Default empty string.
 *     @type  string      $sep    Separates each taxonomy. Default is a space.
 *     @type  string      $after  Displays after the taxonomies. Default empty string.
 * }
-* @param array $args See {@link get_the_taxonomies()} for a description of arguments and their defaults.
 */
 function the_taxonomies( $args = array() ) {
 	$defaults = array(
 		'post' => 0,
 		'before' => '',
 *
 * @since 2.5.0
 *
 * @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global $post.
 * @param array $args {
-*     Arguments about how to format the list of taxonomies.
+*     Optional. Arguments about how to format the list of taxonomies. Default empty array.
 *
 *     @type string $template      Template for displaying a taxonomy label and list of terms.
 *                                 Default is "Label: Terms."
 *     @type string $term_template Template for displaying a single term in the list. Default is the term name
 *                                 linked to its archive.
 * Retrieve all taxonomies of a post with just the names.
 *
 * @since 2.5.0
 *
 * @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global $post.
-* @return array
+* @return array An array of all taxonomy names for the given post.
 */
 function get_post_taxonomies( $post = 0 ) {
 	$post = get_post( $post );
 	return get_object_taxonomies($post);
 * Terms given as integers will only be checked against the object's terms' term_ids.
 * If no terms are given, determines if object is associated with any terms in the given taxonomy.
 *
 * @since 2.7.0
 *
-* @param int $object_id ID of the object (post ID, link ID, ...)
+* @param int              $object_id ID of the object (post ID, link ID, ...).
-* @param string $taxonomy Single taxonomy name
+* @param string           $taxonomy  Single taxonomy name.
-* @param int|string|array $terms Optional. Term term_id, name, slug or array of said
+* @param int|string|array $terms     Optional. Term term_id, name, slug or array of said. Default null.
 * @return bool|WP_Error WP_Error on input error.
 */
 function is_object_in_term( $object_id, $taxonomy, $terms = null ) {
 	if ( !$object_id = (int) $object_id )
-		return new WP_Error( 'invalid_object', __( 'Invalid object ID' ) );
+		return new WP_Error( 'invalid_object', __( 'Invalid object ID.' ) );
 	$object_terms = get_object_term_cache( $object_id, $taxonomy );
-	if ( false === $object_terms )
+	if ( false === $object_terms ) {
-		 $object_terms = wp_get_object_terms( $object_id, $taxonomy );
+		$object_terms = wp_get_object_terms( $object_id, $taxonomy, array( 'update_term_meta_cache' => false ) );
+		if ( is_wp_error( $object_terms ) ) {
+			return $object_terms;
+		}
+		wp_cache_set( $object_id, wp_list_pluck( $object_terms, 'term_id' ), "{$taxonomy}_relationships" );
+	}
 	if ( is_wp_error( $object_terms ) )
 		return $object_terms;
 	if ( empty( $object_terms ) )
 		return false;
 /**
 * Determine if the given object type is associated with the given taxonomy.
 *
 * @since 3.0.0
 *
-* @param string $object_type Object type string
+* @param string $object_type Object type string.
-* @param string $taxonomy Single taxonomy name
+* @param string $taxonomy    Single taxonomy name.
 * @return bool True if object is associated with the taxonomy, otherwise false.
 */
-function is_object_in_taxonomy($object_type, $taxonomy) {
+function is_object_in_taxonomy( $object_type, $taxonomy ) {
-	$taxonomies = get_object_taxonomies($object_type);
+	$taxonomies = get_object_taxonomies( $object_type );
+	if ( empty( $taxonomies ) ) {
-	if ( empty($taxonomies) )
 		return false;
+	}
-	if ( in_array($taxonomy, $taxonomies) )
+	return in_array( $taxonomy, $taxonomies );
-		return true;
-	return false;
 }
 /**
 * Get an array of ancestor IDs for a given object.
 *
 	} elseif ( 'post_type' === $resource_type ) {
 		$ancestors = get_post_ancestors($object_id);
 	}
 	/**
-	 * Filter a given object's ancestors.
+	 * Filters a given object's ancestors.
 	 *
 	 * @since 3.1.0
-	 * @since 4.1.0 Introduced the `$resource_type` parameter.
+	 * @since 4.1.1 Introduced the `$resource_type` parameter.
 	 *
 	 * @param array  $ancestors     An array of object ancestors.
 	 * @param int    $object_id     Object ID.
 	 * @param string $object_type   Type of object.
 	 * @param string $resource_type Type of resource $object_type is.
 	 */
 	return apply_filters( 'get_ancestors', $ancestors, $object_id, $object_type, $resource_type );
 }
 /**
-* Returns the term's parent's term_ID
+* Returns the term's parent's term_ID.
 *
 * @since 3.1.0
 *
-* @param int $term_id
+* @param int    $term_id  Term ID.
-* @param string $taxonomy
+* @param string $taxonomy Taxonomy name.
-*
+* @return int|false False on error.
-* @return int|bool false on error
 */
 function wp_get_term_taxonomy_parent_id( $term_id, $taxonomy ) {
 	$term = get_term( $term_id, $taxonomy );
-	if ( !$term || is_wp_error( $term ) )
+	if ( ! $term || is_wp_error( $term ) ) {
 		return false;
+	}
 	return (int) $term->parent;
 }
 /**
 * Checks the given subset of the term hierarchy for hierarchy loops.
 * Prevents loops from forming and breaks those that it finds.
 *
-* Attached to the wp_update_term_parent filter.
+* Attached to the {@see 'wp_update_term_parent'} filter.
 *
 * @since 3.1.0
 *
-* @param int $parent term_id of the parent for the term we're checking.
+* @param int    $parent   `term_id` of the parent for the term we're checking.
-* @param int $term_id The term we're checking.
+* @param int    $term_id  The term we're checking.
 * @param string $taxonomy The taxonomy of the term we're checking.
 *
 * @return int The new parent for the term.
 */
 function wp_check_term_hierarchy_for_loops( $parent, $term_id, $taxonomy ) {
 	// Nothing fancy here - bail
 	if ( !$parent )
 		return 0;
-	// Can't be its own parent
+	// Can't be its own parent.
 	if ( $parent == $term_id )
 		return 0;
-	// Now look for larger loops
+	// Now look for larger loops.
 	if ( !$loop = wp_find_hierarchy_loop( 'wp_get_term_taxonomy_parent_id', $term_id, $parent, array( $taxonomy ) ) )
 		return $parent; // No loop
-	// Setting $parent to the given value causes a loop
+	// Setting $parent to the given value causes a loop.
 	if ( isset( $loop[$term_id] ) )
 		return 0;
 	// There's a loop, but it doesn't contain $term_id. Break the loop.
 	foreach ( array_keys( $loop ) as $loop_member )

changeset 7	cf61fcea0001
parent 5	5e2f62d02dcd
child 9	177826044cd9