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

equal deleted inserted replaced

-:346c88efed21
+:5e2f62d02dcd
 	global $wp_rewrite;
 	if ( ! did_action( 'init' ) ) {
 		$rewrite = array( 'category' => false, 'post_tag' => false, 'post_format' => false );
 	} else {
+		/**
+		 * Filter the post formats rewrite base.
+		 *
+		 * @since 3.1.0
+		 *
+		 * @param string $context Context of the rewrite base. Default 'type'.
+		 */
 		$post_format_base = apply_filters( 'post_format_rewrite_base', 'type' );
 		$rewrite = array(
 			'category' => array(
 				'hierarchical' => true,
 				'slug' => get_option('category_base') ? get_option('category_base') : 'category',
 				'with_front' => ! get_option('category_base') || $wp_rewrite->using_index_permalinks(),
 				'ep_mask' => EP_CATEGORIES,
 			),
 			'post_tag' => array(
+				'hierarchical' => false,
 				'slug' => get_option('tag_base') ? get_option('tag_base') : 'tag',
 				'with_front' => ! get_option('tag_base') || $wp_rewrite->using_index_permalinks(),
 				'ep_mask' => EP_TAGS,
 			),
 			'post_format' => $post_format_base ? array( 'slug' => $post_format_base ) : false,
 		'show_ui' => false,
 		'_builtin' => true,
 		'show_in_nav_menus' => current_theme_supports( 'post-formats' ),
 	) );
 }
-add_action( 'init', 'create_initial_taxonomies', 0 ); // highest priority
 /**
 * Get a list of registered taxonomy objects.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 3.0.0
 * @uses $wp_taxonomies
-* @see register_taxonomy
 *
 * @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 string $operator The logical operation to perform. 'or' means only one element
 *  from the array needs to match; 'and' means all elements must match. The default is 'and'.
 * Return all of the taxonomy names that are of $object_type.
 *
 * It appears that this function can be used to find all of the names inside of
 * $wp_taxonomies global variable.
 *
-* <code><?php $taxonomies = get_object_taxonomies('post'); ?></code> Should
+* `<?php $taxonomies = get_object_taxonomies('post'); ?>` Should
-* result in <code>Array('category', 'post_tag')</code>
+* result in `Array( 'category', 'post_tag' )`
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wp_taxonomies
 *
 * @param array|string|object $object Name of the type of taxonomy object, or an object (row from posts)
 * Retrieves the taxonomy object of $taxonomy.
 *
 * The get_taxonomy function will first check that the parameter string given
 * is a taxonomy object and if it is, it will return it.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
 *
 * @uses $wp_taxonomies
-* @uses taxonomy_exists() Checks whether taxonomy exists
 *
 * @param string $taxonomy Name of taxonomy object to return
 * @return object|bool The Taxonomy Object or false if $taxonomy doesn't exist
 */
 function get_taxonomy( $taxonomy ) {
 /**
 * Checks that the taxonomy name exists.
 *
 * Formerly is_taxonomy(), introduced in 2.3.0.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 3.0.0
 *
 * @uses $wp_taxonomies
 *
 * @param string $taxonomy Name of taxonomy object
 * Checks to make sure that the taxonomy is an object first. Then Gets the
 * object, and finally returns the hierarchical value in the object.
 *
 * A false return value might also mean that the taxonomy does not exist.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-*
-* @uses taxonomy_exists() Checks whether taxonomy exists
-* @uses get_taxonomy() Used to get the taxonomy object
 *
 * @param string $taxonomy Name of taxonomy object
 * @return bool Whether the taxonomy is hierarchical
 */
 function is_taxonomy_hierarchical($taxonomy) {
 *     * 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.
+* - 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 - Where to show the taxonomy in the admin menu.
+* - 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.
-* - meta_box_cb - Provide a callback function for the meta box display. Defaults to
+* - show_in_quick_edit - Whether to show the taxonomy in the quick/bulk edit panel.
-*     post_categories_meta_box for hierarchical taxonomies and post_tags_meta_box for non-hierarchical.
+*     * 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
 *       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
-* @uses $wp_taxonomies Inserts new taxonomy object into the list
+* @since 4.2.0 Introduced `show_in_quick_edit` argument.
-* @uses $wp Adds query vars
+*
+* @global array $wp_taxonomies Registered taxonomies.
+* @global WP    $wp            WP instance.
 *
 * @param string $taxonomy Taxonomy key, must not exceed 32 characters.
 * @param array|string $object_type Name of the object type for the taxonomy object.
 * @param array|string $args See optional args description above.
 * @return null|WP_Error WP_Error if errors, otherwise null.
 		'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 ( strlen( $taxonomy ) > 32 )
+	if ( empty( $taxonomy ) || strlen( $taxonomy ) > 32 ) {
-		return new WP_Error( 'taxonomy_too_long', __( 'Taxonomies cannot exceed 32 characters in length' ) );
+		_doing_it_wrong( __FUNCTION__, __( 'Taxonomy names must be between 1 and 32 characters in length.' ), '4.2' );
+		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 ) ) {
 		if ( true === $args['query_var'] )
 			$args['query_var'] = $taxonomy;
 		else
 		$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',
 	$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 );
 }
 /**
 * Builds an object with all taxonomy labels out of a taxonomy object
 *
 * Accepted keys of the label array in the taxonomy object:
+*
 * - name - general name for the taxonomy, usually plural. The same as and overridden by $tax->label. Default is Tags/Categories
 * - singular_name - name for one object of this taxonomy. Default is Tag/Category
 * - search_items - Default is Search Tags/Search Categories
 * - popular_items - This string isn't used on hierarchical taxonomies. Default is Popular Tags
 * - 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
-* - parent_item_colon - The same as <code>parent_item</code>, but with colon <code>:</code> in the end
+* - parent_item_colon - The same as `parent_item`, but with colon `:` in the end
 * - edit_item - Default is Edit Tag/Edit Category
 * - view_item - Default is View Tag/View Category
 * - update_item - Default is Update Tag/Update Category
 * - add_new_item - Default is Add New Tag/Add New Category
 * - 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.
 * - 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 - This string isn't used on hierarchical taxonomies. Default is "No tags found", used in the meta box.
+* - not_found - Default is "No tags found"/"No categories found", used in the meta box and taxonomy list table.
 *
 * Above, the first default value is for non-hierarchical taxonomies (like tags) and the second one is for hierarchical taxonomies (like categories).
 *
 * @since 3.0.0
 * @param object $tax Taxonomy object
 		'add_new_item' => array( __( 'Add New Tag' ), __( 'Add New Category' ) ),
 		'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.' ), null ),
+		'not_found' => array( __( 'No tags found.' ), __( 'No categories found.' ) ),
 	);
 	$nohier_vs_hier_defaults['menu_name'] = $nohier_vs_hier_defaults['name'];
 	return _get_custom_object_labels( $tax, $nohier_vs_hier_defaults );
 }
 /**
 * Add an already registered taxonomy to an object type.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 3.0.0
 * @uses $wp_taxonomies Modifies taxonomy object
 *
 * @param string $taxonomy Name of taxonomy object
 * @param string $object_type Name of the object type
 *
 * It is possible to change the order that object_ids is returned by either
 * using PHP sort family functions or using the database by using $args with
 * either ASC or DESC array. The value should be in the key named 'order'.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
 *
-* @uses $wpdb
+* @global wpdb $wpdb WordPress database abstraction object.
-* @uses wp_parse_args() Creates an array from string $args.
 *
 * @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 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
 *	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( $term_ids ) )
+	if ( ! is_array( $term_ids ) ) {
 		$term_ids = array( $term_ids );
+	}
-	if ( ! is_array( $taxonomies ) )
+	if ( ! is_array( $taxonomies ) ) {
 		$taxonomies = array( $taxonomies );
+	}
 	foreach ( (array) $taxonomies as $taxonomy ) {
-		if ( ! taxonomy_exists( $taxonomy ) )
+		if ( ! taxonomy_exists( $taxonomy ) ) {
 			return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy' ) );
+		}
 	}
 	$defaults = array( 'order' => 'ASC' );
 	$args = wp_parse_args( $args, $defaults );
-	extract( $args, EXTR_SKIP );
+	$order = ( 'desc' == strtolower( $args['order'] ) ) ? 'DESC' : 'ASC';
-	$order = ( 'desc' == strtolower( $order ) ) ? 'DESC' : 'ASC';
 	$term_ids = array_map('intval', $term_ids );
 	$taxonomies = "'" . implode( "', '", $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");
-	if ( ! $object_ids )
+	if ( ! $object_ids ){
 		return array();
+	}
 	return $object_ids;
 }
 /**
 * Given a taxonomy query, generates SQL to be appended to a main query.
 	$tax_query_obj = new WP_Tax_Query( $tax_query );
 	return $tax_query_obj->get_sql( $primary_table, $primary_id_column );
 }
 /**
-* Container class for a multiple taxonomy query.
+* 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 {
 	/**
-	 * List of taxonomy queries. A single taxonomy query is an associative array:
+	 * Array of taxonomy queries.
-	 * - 'taxonomy' string The taxonomy being queried
+	 *
-	 * - 'terms' string|array The list of terms
+	 * See {@see WP_Tax_Query::__construct()} for information on tax query arguments.
-	 * - 'field' string (optional) Which term field is being used.
-	 *		Possible values: 'term_id', 'slug' or 'name'
-	 *		Default: 'term_id'
-	 * - 'operator' string (optional)
-	 *		Possible values: 'AND', 'IN' or 'NOT IN'.
-	 *		Default: 'IN'
-	 * - 'include_children' bool (optional) Whether to include child terms.
-	 *		Default: true
 	 *
 	 * @since 3.1.0
 	 * @access public
 	 * @var array
 	 */
 	 *
 	 * @since 3.2.0
 	 * @access private
 	 * @var string
 	 */
-	private static $no_results = array( 'join' => '', 'where' => ' AND 0 = 1' );
+	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 $primary_id_column;
 	/**
 	 * Constructor.
 	 *
-	 * Parses a compact tax query and sets defaults.
-	 *
 	 * @since 3.1.0
+	 * @since 4.1.0 Added support for `$operator` 'NOT EXISTS' and 'EXISTS' values.
 	 * @access public
 	 *
-	 * @param array $tax_query A compact tax query:
+	 * @param array $tax_query {
-	 *  array(
+	 *     Array of taxonomy query clauses.
-	 *    'relation' => 'OR',
+	 *
-	 *    array(
+	 *     @type string $relation Optional. The MySQL keyword used to join
-	 *      'taxonomy' => 'tax1',
+	 *                            the clauses of the query. Accepts 'AND', or 'OR'. Default 'AND'.
-	 *      'terms' => array( 'term1', 'term2' ),
+	 *     @type array {
-	 *      'field' => 'slug',
+	 *         Optional. An array of first-order clause parameters, or another fully-formed tax query.
-	 *    ),
+	 *
-	 *    array(
+	 *         @type string           $taxonomy         Taxonomy being queried. Optional when field=term_taxonomy_id.
-	 *      'taxonomy' => 'tax2',
+	 *         @type string|int|array $terms            Term or terms to filter by.
-	 *      'terms' => array( 'term-a', 'term-b' ),
+	 *         @type string           $field            Field to match $terms against. Accepts 'term_id', 'slug',
-	 *      'field' => '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'] ) && strtoupper( $tax_query['relation'] ) == 'OR' ) {
+		if ( isset( $tax_query['relation'] ) ) {
-			$this->relation = 'OR';
+			$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(),
-			'include_children' => true,
 			'field' => 'term_id',
 			'operator' => 'IN',
+			'include_children' => true,
 		);
-		foreach ( $tax_query as $query ) {
+		foreach ( $queries as $key => $query ) {
-			if ( ! is_array( $query ) )
+			if ( 'relation' === $key ) {
-				continue;
+				$cleaned_query['relation'] = $this->sanitize_relation( $query );
-			$query = array_merge( $defaults, $query );
+			// First-order clause.
+			} elseif ( self::is_first_order_clause( $query ) ) {
-			$query['terms'] = (array) $query['terms'];
+				$cleaned_clause = array_merge( $defaults, $query );
-			$this->queries[] = $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
+	 * @param string $primary_table     Database table where the object being filtered is stored (eg wp_users).
-	 * @param string $primary_id_column
+	 * @param string $primary_id_column ID column for the filtered object in $primary_table.
-	 * @return array
+	 * @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 = '';
-		$where = array();
-		$i = 0;
+		$this->clean_query( $clause );
-		$count = count( $this->queries );
+		if ( is_wp_error( $clause ) ) {
-		foreach ( $this->queries as $index => $query ) {
+			return self::$no_results;
-			$this->clean_query( $query );
+		}
-			if ( is_wp_error( $query ) )
+		$terms = $clause['terms'];
+		$operator = strtoupper( $clause['operator'] );
+		if ( 'IN' == $operator ) {
+			if ( empty( $terms ) ) {
 				return self::$no_results;
+			}
-			extract( $query );
+			$terms = implode( ',', $terms );
-			if ( 'IN' == $operator ) {
+			/*
-				if ( empty( $terms ) ) {
+			 * Before creating another table join, see if this clause has a
-					if ( 'OR' == $this->relation ) {
+			 * sibling with an existing join that can be shared.
-						if ( ( $index + 1 === $count ) && empty( $where ) )
+			 */
-							return self::$no_results;
+			$alias = $this->find_compatible_table_alias( $clause, $parent_query );
-						continue;
+			if ( false === $alias ) {
-					} else {
+				$i = count( $this->table_aliases );
-						return self::$no_results;
-					}
-				}
-				$terms = implode( ',', $terms );
 				$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" : '';
-				$join .= " ON ($primary_table.$primary_id_column = $alias.object_id)";
+				$join .= " ON ($this->primary_table.$this->primary_id_column = $alias.object_id)";
-				$where[] = "$alias.term_taxonomy_id $operator ($terms)";
-			} elseif ( 'NOT IN' == $operator ) {
-				if ( empty( $terms ) )
-					continue;
-				$terms = implode( ',', $terms );
-				$where[] = "$primary_table.$primary_id_column NOT IN (
-					SELECT object_id
-					FROM $wpdb->term_relationships
-					WHERE term_taxonomy_id IN ($terms)
-				)";
-			} elseif ( 'AND' == $operator ) {
-				if ( empty( $terms ) )
-					continue;
-				$num_terms = count( $terms );
-				$terms = implode( ',', $terms );
-				$where[] = "(
-					SELECT COUNT(1)
-					FROM $wpdb->term_relationships
-					WHERE term_taxonomy_id IN ($terms)
-					AND object_id = $primary_table.$primary_id_column
-				) = $num_terms";
 			}
-			$i++;
-		}
+			$where = "$alias.term_taxonomy_id $operator ($terms)";
-		if ( ! empty( $where ) )
+		} elseif ( 'NOT IN' == $operator ) {
-			$where = ' AND ( ' . implode( " $this->relation ", $where ) . ' )';
-		else
+			if ( empty( $terms ) ) {
-			$where = '';
+				return $sql;
+			}
-		return compact( 'join', 'where' );
+			$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
+	 * @param array &$query The single query.
 	 */
 	private function clean_query( &$query ) {
-		if ( ! taxonomy_exists( $query['taxonomy'] ) ) {
+		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) $query['terms'] );
 	/**
 	 * Transforms a single query, from one field to another.
 	 *
 	 * @since 3.2.0
 	 *
-	 * @param array &$query The single query
+	 * @param array  &$query          The single query.
-	 * @param string $resulting_field The resulting field
+	 * @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'] ) )
 		$resulting_field = sanitize_key( $resulting_field );
 		switch ( $query['field'] ) {
 			case 'slug':
 			case 'name':
-				$terms = "'" . implode( "','", array_map( 'sanitize_title_for_query', $query['terms'] ) ) . "'";
+				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']}'
 * '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.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
 *
-* @uses $wpdb
+* @global wpdb $wpdb WordPress database abstraction object.
-* @uses sanitize_term() Cleanses the term based on $filter context before returning.
 * @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 string $taxonomy Taxonomy name that $term is part of.
 * @param string $output Constant OBJECT, ARRAY_A, or ARRAY_N
 * @return mixed|null|WP_Error Term Row from database. Will return null if $term is empty. If taxonomy does not
 * exist then WP_Error will be returned.
 */
 function get_term($term, $taxonomy, $output = OBJECT, $filter = 'raw') {
 	global $wpdb;
-	$null = null;
 	if ( empty($term) ) {
 		$error = new WP_Error('invalid_term', __('Empty Term'));
 		return $error;
 	}
 		$error = new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));
 		return $error;
 	}
 	if ( is_object($term) && empty($term->filter) ) {
-		wp_cache_add($term->term_id, $term, $taxonomy);
+		wp_cache_add( $term->term_id, $term, $taxonomy );
 		$_term = $term;
 	} else {
 		if ( is_object($term) )
 			$term = $term->term_id;
 		if ( !$term = (int) $term )
-			return $null;
+			return null;
-		if ( ! $_term = wp_cache_get($term, $taxonomy) ) {
+		if ( ! $_term = wp_cache_get( $term, $taxonomy ) ) {
 			$_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) );
 			if ( ! $_term )
-				return $null;
+				return null;
-			wp_cache_add($term, $_term, $taxonomy);
+			wp_cache_add( $term, $_term, $taxonomy );
 		}
 	}
-	$_term = apply_filters('get_term', $_term, $taxonomy);
+	/**
-	$_term = apply_filters("get_$taxonomy", $_term, $taxonomy);
+	 * Filter a term.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param int|object $_term    Term object or ID.
+	 * @param string     $taxonomy The taxonomy slug.
+	 */
+	$_term = apply_filters( 'get_term', $_term, $taxonomy );
+	/**
+	 * Filter a taxonomy.
+	 *
+	 * The dynamic portion of the filter name, `$taxonomy`, refers
+	 * to the taxonomy slug.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param int|object $_term    Term object or ID.
+	 * @param string     $taxonomy The taxonomy slug.
+	 */
+	$_term = apply_filters( "get_$taxonomy", $_term, $taxonomy );
 	$_term = sanitize_term($_term, $taxonomy, $filter);
 	if ( $output == OBJECT ) {
 		return $_term;
 	} elseif ( $output == ARRAY_A ) {
 * 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.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
 *
-* @uses $wpdb
+* @global wpdb $wpdb WordPress database abstraction object.
-* @uses sanitize_term() Cleanses the term based on $filter context before returning.
 * @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|int $value Search for this term value
 * @param string $taxonomy Taxonomy Name
 	if ( 'slug' == $field ) {
 		$field = 't.slug';
 		$value = sanitize_title($value);
 		if ( empty($value) )
 			return false;
-	} else if ( 'name' == $field ) {
+	} elseif ( 'name' == $field ) {
 		// Assume already escaped
 		$value = wp_unslash($value);
 		$field = 't.name';
-	} else if ( 'term_taxonomy_id' == $field ) {
+	} elseif ( 'term_taxonomy_id' == $field ) {
 		$value = (int) $value;
 		$field = 'tt.term_taxonomy_id';
 	} else {
-		$term = get_term( (int) $value, $taxonomy, $output, $filter);
+		$term = get_term( (int) $value, $taxonomy, $output, $filter );
 		if ( is_wp_error( $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) );
+	$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, $value ) );
-	if ( !$term )
+	if ( ! $term )
 		return false;
-	wp_cache_add($term->term_id, $term, $taxonomy);
+	wp_cache_add( $term->term_id, $term, $taxonomy );
-	$term = apply_filters('get_term', $term, $taxonomy);
+	/** This filter is documented in wp-includes/taxonomy.php */
-	$term = apply_filters("get_$taxonomy", $term, $taxonomy);
+	$term = apply_filters( 'get_term', $term, $taxonomy );
+	/** This filter is documented in wp-includes/taxonomy.php */
+	$term = apply_filters( "get_$taxonomy", $term, $taxonomy );
 	$term = sanitize_term($term, $taxonomy, $filter);
 	if ( $output == OBJECT ) {
 		return $term;
 	} elseif ( $output == ARRAY_A ) {
 * This recursive function will merge all of the children of $term into the same
 * array of term IDs. Only useful for taxonomies which are hierarchical.
 *
 * Will return an empty array if $term does not exist in $taxonomy.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
 *
-* @uses $wpdb
+* @global wpdb $wpdb WordPress database abstraction object.
-* @uses _get_term_hierarchy()
-* @uses get_term_children() Used to get the children of both $taxonomy and the parent $term
 *
 * @param string $term_id ID of Term to get children
 * @param string $taxonomy Taxonomy Name
-* @return array|WP_Error List of Term Objects. WP_Error returned if $taxonomy does not exist
+* @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) )
 		return new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));
 		return array();
 	$children = $terms[$term_id];
 	foreach ( (array) $terms[$term_id] as $child ) {
+		if ( $term_id == $child ) {
+			continue;
+		}
 		if ( isset($terms[$child]) )
 			$children = array_merge($children, get_term_children($child, $taxonomy));
 	}
 	return $children;
 *
 * Does checks for $term, based on the $taxonomy. The function is for contextual
 * reasons and for simplicity of usage. See sanitize_term_field() for more
 * information.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-*
-* @uses sanitize_term_field() Passes the return value in sanitize_term_field on success.
 *
 * @param string $field Term field to fetch
 * @param int $term Term ID
 * @param string $taxonomy Taxonomy Name
 * @param string $context Optional, default is display. Look at sanitize_term_field() for available options.
 * Sanitizes Term for editing.
 *
 * Return value is sanitize_term() and usage is for sanitizing the term for
 * editing. Function is for contextual and simplicity.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-*
-* @uses sanitize_term() Passes the return value on success
 *
 * @param int|object $id Term ID or Object
 * @param string $taxonomy Taxonomy Name
 * @return mixed|null|WP_Error Will return empty string if $term is not an object.
 */
 * the $args.
 *
 * The 'get_terms_orderby' filter passes the ORDER BY clause for the query
 * along with the $args array.
 *
-* The 'get_terms_fields' filter passes the fields for the SELECT query
-* along with the $args array.
-*
-* The list of arguments that $args can contain, which will overwrite the defaults:
-*
-* orderby - Default is 'name'. Can be name, count, term_group, slug or nothing
-* (will use term_id), Passing a custom value other than these will cause it to
-* order based on the custom value.
-*
-* order - Default is ASC. Can use DESC.
-*
-* hide_empty - Default is true. Will not return empty terms, which means
-* terms whose count is 0 according to the given taxonomy.
-*
-* exclude - Default is an empty array. An array, comma- or space-delimited string
-* of term ids to exclude from the return array. If 'include' is non-empty,
-* 'exclude' is ignored.
-*
-* exclude_tree - Default is an empty array. An array, comma- or space-delimited
-* string of term ids to exclude from the return array, along with all of their
-* descendant terms according to the primary taxonomy. If 'include' is non-empty,
-* 'exclude_tree' is ignored.
-*
-* include - Default is an empty array. An array, comma- or space-delimited string
-* of term ids to include in the return array.
-*
-* number - The maximum number of terms to return. Default is to return them all.
-*
-* offset - The number by which to offset the terms query.
-*
-* fields - Default is 'all', which returns an array of term objects.
-* If 'fields' is 'ids' or 'names', returns an array of
-* integers or strings, respectively.
-*
-* slug - Returns terms whose "slug" matches this value. Default is empty string.
-*
-* hierarchical - Whether to include terms that have non-empty descendants
-* (even if 'hide_empty' is set to true).
-*
-* search - Returned terms' names will contain the value of 'search',
-* case-insensitive. Default is an empty string.
-*
-* name__like - Returned terms' names will contain the value of 'name__like',
-* case-insensitive. Default is empty string.
-*
-* description__like - Returned terms' descriptions will contain the value of
-*  'description__like', case-insensitive. Default is empty string.
-*
-* The argument 'pad_counts', if set to true will include the quantity of a term's
-* children in the quantity of each term's "count" object variable.
-*
-* The 'get' argument, if set to 'all' instead of its default empty string,
-* returns terms regardless of ancestry or whether the terms are empty.
-*
-* The 'child_of' argument, when used, should be set to the integer of a term ID. Its default
-* is 0. If set to a non-zero value, all returned terms will be descendants
-* of that term according to the given taxonomy. Hence 'child_of' is set to 0
-* if more than one taxonomy is passed in $taxonomies, because multiple taxonomies
-* make term ancestry ambiguous.
-*
-* The 'parent' argument, when used, should be set to the integer of a term ID. Its default is
-* the empty string '', which has a different meaning from the integer 0.
-* If set to an integer value, all returned terms will have as an immediate
-* ancestor the term whose ID is specified by that integer according to the given taxonomy.
-* The 'parent' argument is different from 'child_of' in that a term X is considered a 'parent'
-* of term Y only if term X is the father of term Y, not its grandfather or great-grandfather, etc.
-*
-* The 'cache_domain' argument enables a unique cache key to be produced when this query is stored
-* in object cache. For instance, if you are using one of this function's filters to modify the
-* query (such as 'terms_clauses'), setting 'cache_domain' to a unique value will not overwrite
-* the cache for similar queries. Default value is 'core'.
-*
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-*
+* @since 4.2.0 Introduced 'name' and 'childless' parameters.
-* @uses $wpdb
+*
-* @uses wp_parse_args() Merges the defaults with those defined by $args and allows for strings.
+* @global wpdb $wpdb WordPress database abstraction object.
 *
-* @param string|array $taxonomies Taxonomy name or list of Taxonomy names
+* @param string|array $taxonomies Taxonomy name or list of Taxonomy names.
-* @param string|array $args The values of what to search for when returning terms
+* @param array|string $args {
-* @return array|WP_Error List of Term Objects and their children. Will return WP_Error, if any of $taxonomies do not exist.
+*     Optional. Array or string of arguments to get terms.
-*/
+*
-function get_terms($taxonomies, $args = '') {
+*     @type string       $orderby           Field(s) to order terms by. Accepts term fields ('name', 'slug',
+*                                           'term_group', 'term_id', 'id', 'description'), 'count' for term
+*                                           taxonomy count, 'include' to match the 'order' of the $include param,
+*                                           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();
 	$single_taxonomy = ! is_array( $taxonomies ) || 1 === count( $taxonomies );
-	if ( ! is_array( $taxonomies ) )
+	if ( ! is_array( $taxonomies ) ) {
 		$taxonomies = array( $taxonomies );
+	}
 	foreach ( $taxonomies as $taxonomy ) {
 		if ( ! taxonomy_exists($taxonomy) ) {
 			$error = new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));
 			return $error;
 		}
 	}
 	$defaults = array('orderby' => 'name', 'order' => 'ASC',
 		'hide_empty' => true, 'exclude' => array(), 'exclude_tree' => array(), 'include' => array(),
-		'number' => '', 'fields' => 'all', 'slug' => '', 'parent' => '',
+		'number' => '', 'fields' => 'all', 'name' => '', 'slug' => '', 'parent' => '', 'childless' => false,
 		'hierarchical' => true, 'child_of' => 0, 'get' => '', 'name__like' => '', 'description__like' => '',
 		'pad_counts' => false, 'offset' => '', 'search' => '', 'cache_domain' => 'core' );
 	$args = wp_parse_args( $args, $defaults );
 	$args['number'] = absint( $args['number'] );
 	$args['offset'] = absint( $args['offset'] );
-	if ( !$single_taxonomy || ! is_taxonomy_hierarchical( reset( $taxonomies ) ) ||
-		'' !== $args['parent'] ) {
+	// Save queries by not crawling the tree in the case of multiple taxes or a flat tax.
-		$args['child_of'] = 0;
+	$has_hierarchical_tax = false;
+	foreach ( $taxonomies as $_tax ) {
+		if ( is_taxonomy_hierarchical( $_tax ) ) {
+			$has_hierarchical_tax = true;
+		}
+	}
+	if ( ! $has_hierarchical_tax ) {
 		$args['hierarchical'] = false;
 		$args['pad_counts'] = false;
 	}
+	// '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, $taxonomies );
-	extract($args, EXTR_SKIP);
+	// Avoid the query if the queried parent/child_of term has no descendants.
+	$child_of = $args['child_of'];
+	$parent   = $args['parent'];
 	if ( $child_of ) {
-		$hierarchy = _get_term_hierarchy( reset( $taxonomies ) );
+		$_parent = $child_of;
-		if ( ! isset( $hierarchy[ $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;
-	}
+		}
-	if ( $parent ) {
-		$hierarchy = _get_term_hierarchy( reset( $taxonomies ) );
-		if ( ! isset( $hierarchy[ $parent ] ) )
-			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']) : '';
-	$key = md5( serialize( compact(array_keys($defaults)) ) . serialize( $taxonomies ) . $filter_key );
+	$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 ) {
-		$cache = apply_filters('get_terms', $cache, $taxonomies, $args);
+		/**
+		 * 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;
 	}
-	$_orderby = strtolower($orderby);
+	$_orderby = strtolower( $args['orderby'] );
-	if ( 'count' == $_orderby )
+	if ( 'count' == $_orderby ) {
 		$orderby = 'tt.count';
-	else if ( 'name' == $_orderby )
+	} elseif ( 'name' == $_orderby ) {
 		$orderby = 't.name';
-	else if ( 'slug' == $_orderby )
+	} elseif ( 'slug' == $_orderby ) {
 		$orderby = 't.slug';
-	else if ( 'term_group' == $_orderby )
+	} 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';
-	else if ( 'none' == $_orderby )
+	} elseif ( 'description' == $_orderby ) {
+		$orderby = 'tt.description';
+	} elseif ( 'none' == $_orderby ) {
 		$orderby = '';
-	elseif ( empty($_orderby) || 'id' == $_orderby )
+	} elseif ( empty($_orderby) || 'id' == $_orderby ) {
 		$orderby = 't.term_id';
-	else
+	} 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, $taxonomies );
-	if ( !empty($orderby) )
+	$order = strtoupper( $args['order'] );
+	if ( ! empty( $orderby ) ) {
 		$orderby = "ORDER BY $orderby";
-	else
+	} else {
 		$order = '';
+	}
-	$order = strtoupper( $order );
-	if ( '' !== $order && !in_array( $order, array( 'ASC', 'DESC' ) ) )
+	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 = '';
+	$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 = implode( ',', array_map( 'intval', $excluded_children ) );
+		$exclusions = array_merge( $excluded_children, $exclusions );
 	}
 	if ( ! empty( $exclude ) ) {
-		$exterms = wp_parse_id_list( $exclude );
+		$exclusions = array_merge( wp_parse_id_list( $exclude ), $exclusions );
-		if ( empty( $exclusions ) )
+	}
-			$exclusions = implode( ',', $exterms );
-		else
+	// 'childless' terms are those without an entry in the flattened term hierarchy.
-			$exclusions .= ', ' . implode( ',', $exterms );
+	$childless = (bool) $args['childless'];
-	}
+	if ( $childless ) {
+		foreach ( $taxonomies as $_tax ) {
-	if ( ! empty( $exclusions ) )
+			$term_hierarchy = _get_term_hierarchy( $_tax );
-		$exclusions = ' AND t.term_id NOT IN (' . $exclusions . ')';
+			$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 ) )
+	if ( ! empty( $exclusions ) ) {
 		$where .= $exclusions;
+	}
-	if ( !empty($slug) ) {
-		$slug = sanitize_title($slug);
+	if ( ! empty( $args['name'] ) ) {
-		$where .= " AND t.slug = '$slug'";
+		if ( is_array( $args['name'] ) ) {
-	}
+			$name = array_map( 'sanitize_text_field', $args['name'] );
+			$where .= " AND t.name IN ('" . implode( "', '", array_map( 'esc_sql', $name ) ) . "')";
-	if ( !empty($name__like) ) {
+		} else {
-		$name__like = like_escape( $name__like );
+			$name = sanitize_text_field( $args['name'] );
-		$where .= $wpdb->prepare( " AND t.name LIKE %s", '%' . $name__like . '%' );
+			$where .= $wpdb->prepare( " AND t.name = %s", $name );
-	}
+		}
+	}
-	if ( ! empty( $description__like ) ) {
-		$description__like = like_escape( $description__like );
+	if ( ! empty( $args['slug'] ) ) {
-		$where .= $wpdb->prepare( " AND tt.description LIKE %s", '%' . $description__like . '%' );
+		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'";
 	}
-	if ( 'count' == $fields )
+	$hierarchical = $args['hierarchical'];
+	if ( 'count' == $args['fields'] ) {
 		$hierarchical = false;
+	}
-	if ( $hide_empty && !$hierarchical )
+	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 )
+		if ( $offset ) {
 			$limits = 'LIMIT ' . $offset . ',' . $number;
-		else
+		} else {
 			$limits = 'LIMIT ' . $number;
+		}
 	} else {
 		$limits = '';
 	}
-	if ( ! empty( $search ) ) {
+	if ( ! empty( $args['search'] ) ) {
-		$search = like_escape( $search );
+		$like = '%' . $wpdb->esc_like( $args['search'] ) . '%';
-		$where .= $wpdb->prepare( ' AND ((t.name LIKE %s) OR (t.slug LIKE %s))', '%' . $search . '%', '%' . $search . '%' );
+		$where .= $wpdb->prepare( ' AND ((t.name LIKE %s) OR (t.slug LIKE %s))', $like, $like );
 	}
 	$selects = array();
-	switch ( $fields ) {
+	switch ( $args['fields'] ) {
 		case 'all':
 			$selects = array( 't.*', 'tt.*' );
 			break;
 		case 'ids':
 		case 'id=>parent':
-			$selects = array( 't.term_id', 'tt.parent', 'tt.count' );
+			$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' );
+			$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' );
+			$selects = array( 't.term_id', 't.name', 'tt.count', 'tt.taxonomy' );
 			break;
 		case 'id=>slug':
-			$selects = array( 't.term_id', 't.slug' );
+			$selects = array( 't.term_id', 't.slug', 'tt.count', 'tt.taxonomy' );
 			break;
 	}
-	$_fields = $fields;
+	$_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 );
-	foreach ( $pieces as $piece )
+	$fields = isset( $clauses[ 'fields' ] ) ? $clauses[ 'fields' ] : '';
-		$$piece = isset( $clauses[ $piece ] ) ? $clauses[ $piece ] : '';
+	$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";
-	$fields = $_fields;
+	if ( 'count' == $_fields ) {
-	if ( 'count' == $fields ) {
 		$term_count = $wpdb->get_var($query);
 		return $term_count;
 	}
 	$terms = $wpdb->get_results($query);
-	if ( 'all' == $fields ) {
+	if ( 'all' == $_fields ) {
-		update_term_cache($terms);
+		update_term_cache( $terms );
 	}
 	if ( empty($terms) ) {
 		wp_cache_add( $cache_key, array(), 'terms', DAY_IN_SECONDS );
-		$terms = apply_filters('get_terms', array(), $taxonomies, $args);
+		/** This filter is documented in wp-includes/taxonomy.php */
+		$terms = apply_filters( 'get_terms', array(), $taxonomies, $args );
 		return $terms;
 	}
 	if ( $child_of ) {
-		$children = _get_term_hierarchy( reset( $taxonomies ) );
+		foreach ( $taxonomies as $_tax ) {
-		if ( ! empty( $children ) )
+			$children = _get_term_hierarchy( $_tax );
-			$terms = _get_term_children( $child_of, $terms, reset( $taxonomies ) );
+			if ( ! empty( $children ) ) {
+				$terms = _get_term_children( $child_of, $terms, $_tax );
+			}
+		}
 	}
 	// Update term counts to include children.
-	if ( $pad_counts && 'all' == $fields )
+	if ( $args['pad_counts'] && 'all' == $_fields ) {
-		_pad_term_counts( $terms, reset( $taxonomies ) );
+		foreach ( $taxonomies as $_tax ) {
+			_pad_term_counts( $terms, $_tax );
+		}
+	}
 	// Make sure we show empty categories that have children.
-	if ( $hierarchical && $hide_empty && is_array( $terms ) ) {
+	if ( $hierarchical && $args['hide_empty'] && is_array( $terms ) ) {
 		foreach ( $terms as $k => $term ) {
 			if ( ! $term->count ) {
-				$children = _get_term_children( $term->term_id, $terms, reset( $taxonomies ) );
+				$children = get_term_children( $term->term_id, $term->taxonomy );
-				if ( is_array( $children ) )
+				if ( is_array( $children ) ) {
-					foreach ( $children as $child )
+					foreach ( $children as $child_id ) {
-						if ( $child->count )
+						$child = get_term( $child_id, $term->taxonomy );
+						if ( $child->count ) {
 							continue 2;
+						}
+					}
+				}
 				// It really is empty
 				unset($terms[$k]);
 			}
 		}
 	}
-	reset( $terms );
 	$_terms = array();
-	if ( 'id=>parent' == $fields ) {
+	if ( 'id=>parent' == $_fields ) {
-		while ( $term = array_shift( $terms ) )
+		foreach ( $terms as $term ) {
-			$_terms[$term->term_id] = $term->parent;
+			$_terms[ $term->term_id ] = $term->parent;
-	} elseif ( 'ids' == $fields ) {
+		}
-		while ( $term = array_shift( $terms ) )
+	} elseif ( 'ids' == $_fields ) {
+		foreach ( $terms as $term ) {
 			$_terms[] = $term->term_id;
-	} elseif ( 'names' == $fields ) {
+		}
-		while ( $term = array_shift( $terms ) )
+	} elseif ( 'names' == $_fields ) {
+		foreach ( $terms as $term ) {
 			$_terms[] = $term->name;
-	} elseif ( 'id=>name' == $fields ) {
+		}
-		while ( $term = array_shift( $terms ) )
+	} elseif ( 'id=>name' == $_fields ) {
-			$_terms[$term->term_id] = $term->name;
+		foreach ( $terms as $term ) {
-	} elseif ( 'id=>slug' == $fields ) {
+			$_terms[ $term->term_id ] = $term->name;
-		while ( $term = array_shift( $terms ) )
+		}
-			$_terms[$term->term_id] = $term->slug;
+	} elseif ( 'id=>slug' == $_fields ) {
-	}
+		foreach ( $terms as $term ) {
+			$_terms[ $term->term_id ] = $term->slug;
-	if ( ! empty( $_terms ) )
+		}
+	}
+	if ( ! empty( $_terms ) ) {
 		$terms = $_terms;
+	}
-	if ( $number && is_array( $terms ) && count( $terms ) > $number )
+	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.
 *
 * Formerly is_term(), introduced in 2.3.0.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 3.0.0
 *
-* @uses $wpdb
+* @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param int|string $term The term to check
 * @param string $taxonomy The taxonomy name to use
-* @param int $parent ID of parent term under which to confine the exists search.
+* @param int $parent Optional. ID of parent term under which to confine the exists search.
-* @return mixed Returns 0 if the term does not exist. Returns the term ID if no taxonomy is specified
+* @return mixed Returns null if the term does not exist. Returns the term ID
-* 	and the term ID exists. Returns an array of the term ID and the taxonomy if the pairing exists.
+*               if no taxonomy is specified and the term ID exists. Returns
-*/
+*               an array of the term ID and the term taxonomy ID the taxonomy
-function term_exists($term, $taxonomy = '', $parent = 0) {
+*               is specified and the pairing exists.
+*/
+function term_exists( $term, $taxonomy = '', $parent = null ) {
 	global $wpdb;
 	$select = "SELECT term_id FROM $wpdb->terms as t WHERE ";
 	$tax_select = "SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE ";
 		else
 			return $wpdb->get_var( $wpdb->prepare( $select . $where, $term ) );
 	}
 	$term = trim( wp_unslash( $term ) );
+	$slug = sanitize_title( $term );
-	if ( '' === $slug = sanitize_title($term) )
-		return 0;
 	$where = 't.slug = %s';
 	$else_where = 't.name = %s';
 	$where_fields = array($slug);
 	$else_where_fields = array($term);
+	$orderby = 'ORDER BY t.term_id ASC';
+	$limit = 'LIMIT 1';
 	if ( !empty($taxonomy) ) {
-		$parent = (int) $parent;
+		if ( is_numeric( $parent ) ) {
-		if ( $parent > 0 ) {
+			$parent = (int) $parent;
 			$where_fields[] = $parent;
 			$else_where_fields[] = $parent;
 			$where .= ' AND tt.parent = %d';
 			$else_where .= ' AND tt.parent = %d';
 		}
 		$where_fields[] = $taxonomy;
 		$else_where_fields[] = $taxonomy;
-		if ( $result = $wpdb->get_row( $wpdb->prepare("SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE $where AND tt.taxonomy = %s", $where_fields), ARRAY_A) )
+		if ( $result = $wpdb->get_row( $wpdb->prepare("SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE $where AND tt.taxonomy = %s $orderby $limit", $where_fields), ARRAY_A) )
 			return $result;
-		return $wpdb->get_row( $wpdb->prepare("SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE $else_where AND tt.taxonomy = %s", $else_where_fields), ARRAY_A);
+		return $wpdb->get_row( $wpdb->prepare("SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE $else_where AND tt.taxonomy = %s $orderby $limit", $else_where_fields), ARRAY_A);
 	}
-	if ( $result = $wpdb->get_var( $wpdb->prepare("SELECT term_id FROM $wpdb->terms as t WHERE $where", $where_fields) ) )
+	if ( $result = $wpdb->get_var( $wpdb->prepare("SELECT term_id FROM $wpdb->terms as t WHERE $where $orderby $limit", $where_fields) ) )
 		return $result;
-	return $wpdb->get_var( $wpdb->prepare("SELECT term_id FROM $wpdb->terms as t WHERE $else_where", $else_where_fields) );
+	return $wpdb->get_var( $wpdb->prepare("SELECT term_id FROM $wpdb->terms as t WHERE $else_where $orderby $limit", $else_where_fields) );
 }
 /**
 * Check if a term is an ancestor of another term.
 *
 * this function will sanitize <strong>all</strong> fields. The context is based
 * on sanitize_term_field().
 *
 * The $term is expected to be either an array or an object.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-*
-* @uses sanitize_term_field Used to sanitize all fields in a term
 *
 * @param array|object $term The term to check
 * @param string $taxonomy The taxonomy name to use
 * @param string $context Default is 'display'.
 * @return array|object Term with all fields sanitized
 */
 function sanitize_term($term, $taxonomy, $context = 'display') {
-	if ( 'raw' == $context )
+	$fields = array( 'term_id', 'name', 'description', 'slug', 'count', 'parent', 'term_group', 'term_taxonomy_id', 'object_id' );
-		return $term;
+	$do_object = is_object( $term );
-	$fields = array('term_id', 'name', 'description', 'slug', 'count', 'parent', 'term_group');
-	$do_object = false;
-	if ( is_object($term) )
-		$do_object = true;
 	$term_id = $do_object ? $term->term_id : (isset($term['term_id']) ? $term['term_id'] : 0);
 	foreach ( (array) $fields as $field ) {
 		if ( $do_object ) {
 *
 * There are enough filters for each context to support a custom filtering
 * without creating your own filter function. Simply create a function that
 * hooks into the filter you need.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
 *
-* @uses $wpdb
+* @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param string $field Term field to sanitize
 * @param string $value Search for this term value
 * @param int $term_id Term ID
 * @param string $taxonomy Taxonomy Name
 * @param string $context Either edit, db, display, attribute, or js.
 * @return mixed sanitized field
 */
 function sanitize_term_field($field, $value, $term_id, $taxonomy, $context) {
-	if ( 'parent' == $field  || 'term_id' == $field || 'count' == $field || 'term_group' == $field ) {
+	$int_fields = array( 'parent', 'term_id', 'count', 'term_group', 'term_taxonomy_id', 'object_id' );
+	if ( in_array( $field, $int_fields ) ) {
 		$value = (int) $value;
 		if ( $value < 0 )
 			$value = 0;
 	}
 	if ( 'raw' == $context )
 		return $value;
 	if ( 'edit' == $context ) {
-		$value = apply_filters("edit_term_{$field}", $value, $term_id, $taxonomy);
-		$value = apply_filters("edit_{$taxonomy}_{$field}", $value, $term_id);
+		/**
+		 * Filter a term field to edit before it is sanitized.
+		 *
+		 * The dynamic portion of the filter name, `$field`, refers to the term field.
+		 *
+		 * @since 2.3.0
+		 *
+		 * @param mixed $value     Value of the term field.
+		 * @param int   $term_id   Term ID.
+		 * @param string $taxonomy Taxonomy slug.
+		 */
+		$value = apply_filters( "edit_term_{$field}", $value, $term_id, $taxonomy );
+		/**
+		 * Filter the taxonomy field to edit before it is sanitized.
+		 *
+		 * The dynamic portions of the filter name, `$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);
-	} else if ( 'db' == $context ) {
+	} elseif ( 'db' == $context ) {
-		$value = apply_filters("pre_term_{$field}", $value, $taxonomy);
-		$value = apply_filters("pre_{$taxonomy}_{$field}", $value);
+		/**
+		 * Filter a term field value before it is sanitized.
+		 *
+		 * The dynamic portion of the filter name, `$field`, refers to the term field.
+		 *
+		 * @since 2.3.0
+		 *
+		 * @param mixed  $value    Value of the term field.
+		 * @param string $taxonomy Taxonomy slug.
+		 */
+		$value = apply_filters( "pre_term_{$field}", $value, $taxonomy );
+		/**
+		 * Filter a taxonomy field before it is sanitized.
+		 *
+		 * The dynamic portions of the filter name, `$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 )
+		if ( 'slug' == $field ) {
-			$value = apply_filters('pre_category_nicename', $value);
+			/**
+			 * Filter the category nicename before it is sanitized.
-	} else if ( 'rss' == $context ) {
+			 *
-		$value = apply_filters("term_{$field}_rss", $value, $taxonomy);
+			 * Use the pre_{$taxonomy}_{$field} hook instead.
-		$value = apply_filters("{$taxonomy}_{$field}_rss", $value);
+			 *
+			 * @since 2.0.3
+			 *
+			 * @param string $value The category nicename.
+			 */
+			$value = apply_filters( 'pre_category_nicename', $value );
+		}
+	} elseif ( 'rss' == $context ) {
+		/**
+		 * Filter the term field for use in RSS.
+		 *
+		 * The dynamic portion of the filter name, `$field`, refers to the term field.
+		 *
+		 * @since 2.3.0
+		 *
+		 * @param mixed  $value    Value of the term field.
+		 * @param string $taxonomy Taxonomy slug.
+		 */
+		$value = apply_filters( "term_{$field}_rss", $value, $taxonomy );
+		/**
+		 * Filter the taxonomy field for use in RSS.
+		 *
+		 * The dynamic portions of the hook name, `$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.
-		$value = apply_filters("term_{$field}", $value, $term_id, $taxonomy, $context);
-		$value = apply_filters("{$taxonomy}_{$field}", $value, $term_id, $context);
+		/**
-	}
+		 * Filter the term field sanitized for display.
+		 *
-	if ( 'attribute' == $context )
+		 * The dynamic portion of the filter name, `$field`, refers to the term field name.
+		 *
+		 * @since 2.3.0
+		 *
+		 * @param mixed  $value    Value of the term field.
+		 * @param int    $term_id  Term ID.
+		 * @param string $taxonomy Taxonomy slug.
+		 * @param string $context  Context to retrieve the term field value.
+		 */
+		$value = apply_filters( "term_{$field}", $value, $term_id, $taxonomy, $context );
+		/**
+		 * Filter the taxonomy field sanitized for display.
+		 *
+		 * The dynamic portions of the filter name, `$taxonomy`, and $field, refer
+		 * to the taxonomy slug and taxonomy field, respectively.
+		 *
+		 * @since 2.3.0
+		 *
+		 * @param mixed  $value   Value of the taxonomy field.
+		 * @param int    $term_id Term ID.
+		 * @param string $context Context to retrieve the taxonomy field value.
+		 */
+		$value = apply_filters( "{$taxonomy}_{$field}", $value, $term_id, $context );
+	}
+	if ( 'attribute' == $context ) {
 		$value = esc_attr($value);
-	else if ( 'js' == $context )
+	} elseif ( 'js' == $context ) {
 		$value = esc_js($value);
+	}
 	return $value;
 }
 /**
 * Count how many terms are in Taxonomy.
 *
 * Default $args is 'hide_empty' which can be 'hide_empty=true' or array('hide_empty' => true).
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-*
-* @uses get_terms()
-* @uses wp_parse_args() Turns strings into arrays and merges defaults into an array.
 *
 * @param string $taxonomy Taxonomy name
 * @param array|string $args Overwrite defaults. See get_terms()
 * @return int|WP_Error How many terms are in $taxonomy. WP_Error if $taxonomy does not exist.
 */
 *
 * Will remove all relationships between the object and any terms in
 * a particular taxonomy or taxonomies. Does not remove the term or
 * taxonomy itself.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-* @uses wp_remove_object_terms()
 *
 * @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 ) {
 * The $args 'default' will only override the terms found, if there is only one
 * 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
-* @package WordPress
+*
-* @subpackage Taxonomy
 * @since 2.3.0
 *
-* @uses $wpdb
+* @global wpdb $wpdb WordPress database abstraction object.
-* @uses do_action() Calls both 'delete_term' and 'delete_$taxonomy' action
-*	hooks, passing term ID, term taxonomy ID, and deleted term object. 'delete_term'
-*	also gets taxonomy as the third parameter.
 *
 * @param int $term Term ID
 * @param string $taxonomy Taxonomy Name
 * @param array|string $args Optional. Change 'default' term id and override found term ids.
 * @return bool|WP_Error Returns false if not term; true if completes delete action.
 		if ( $defaults['default'] == $term )
 			return 0; // Don't delete the default category
 	}
 	$args = wp_parse_args($args, $defaults);
-	extract($args, EXTR_SKIP);
+	if ( isset( $args['default'] ) ) {
-	if ( isset( $default ) ) {
+		$default = (int) $args['default'];
-		$default = (int) $default;
+		if ( ! term_exists( $default, $taxonomy ) ) {
-		if ( ! term_exists($default, $taxonomy) )
+			unset( $default );
-			unset($default);
+		}
 	}
+	if ( isset( $args['force_default'] ) ) {
+		$force_default = $args['force_default'];
+	}
+	/**
+	 * Fires when deleting a term, before any modifications are made to posts or terms.
+	 *
+	 * @since 4.1.0
+	 *
+	 * @param int    $term     Term ID.
+	 * @param string $taxonomy Taxonomy Name.
+	 */
+	do_action( 'pre_delete_term', $term, $taxonomy );
 	// Update children to point to new parent
 	if ( is_taxonomy_hierarchical($taxonomy) ) {
 		$term_obj = get_term($term, $taxonomy);
 		if ( is_wp_error( $term_obj ) )
 			return $term_obj;
 		$parent = $term_obj->parent;
-		$edit_tt_ids = $wpdb->get_col( "SELECT `term_taxonomy_id` FROM $wpdb->term_taxonomy WHERE `parent` = " . (int)$term_obj->term_id );
+		$edit_ids = $wpdb->get_results( "SELECT term_id, term_taxonomy_id FROM $wpdb->term_taxonomy WHERE `parent` = " . (int)$term_obj->term_id );
+		$edit_tt_ids = wp_list_pluck( $edit_ids, 'term_taxonomy_id' );
+		/**
+		 * Fires immediately before a term to delete's children are reassigned a parent.
+		 *
+		 * @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 );
+		/**
+		 * Fires immediately after a term to delete's children are reassigned a parent.
+		 *
+		 * @since 2.9.0
+		 *
+		 * @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 ) );
 		clean_object_term_cache( $objects, $object_type );
 	// Get the object before deletion so we can pass to actions below
 	$deleted_term = get_term( $term, $taxonomy );
+	/**
+	 * Fires immediately before a term taxonomy ID is deleted.
+	 *
+	 * @since 2.9.0
+	 *
+	 * @param int $tt_id Term taxonomy ID.
+	 */
 	do_action( 'delete_term_taxonomy', $tt_id );
 	$wpdb->delete( $wpdb->term_taxonomy, array( 'term_taxonomy_id' => $tt_id ) );
+	/**
+	 * Fires immediately after a term taxonomy ID is deleted.
+	 *
+	 * @since 2.9.0
+	 *
+	 * @param int $tt_id Term taxonomy ID.
+	 */
 	do_action( 'deleted_term_taxonomy', $tt_id );
 	// Delete the term if no taxonomies use it.
 	if ( !$wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM $wpdb->term_taxonomy WHERE term_id = %d", $term) ) )
 		$wpdb->delete( $wpdb->terms, array( 'term_id' => $term ) );
 	clean_term_cache($term, $taxonomy);
+	/**
+	 * Fires after a term is deleted from the database and the cache is cleaned.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @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.
+	 */
 	do_action( 'delete_term', $term, $tt_id, $taxonomy, $deleted_term );
+	/**
+	 * Fires after a term in a specific taxonomy is deleted.
+	 *
+	 * The dynamic portion of the hook name, `$taxonomy`, refers to the specific
+	 * taxonomy the term belonged to.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param int     $term         Term ID.
+	 * @param int     $tt_id        Term taxonomy ID.
+	 * @param mixed   $deleted_term Copy of the already-deleted term, in the form specified
+	 *                              by the parent function. {@see WP_Error} otherwise.
+	 */
 	do_action( "delete_$taxonomy", $term, $tt_id, $deleted_term );
 	return true;
 }
 /**
 * Deletes one existing category.
 *
 * @since 2.0.0
-* @uses wp_delete_term()
 *
 * @param int $cat_ID
 * @return mixed 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.
 */
 }
 /**
 * Retrieves the terms associated with the given object(s), in the supplied taxonomies.
 *
-* The following information has to do the $args parameter and for what can be
-* contained in the string or array of that parameter, if it exists.
-*
-* The first argument is called, 'orderby' and has the default value of 'name'.
-* The other value that is supported is 'count'.
-*
-* The second argument is called, 'order' and has the default value of 'ASC'.
-* The only other value that will be acceptable is 'DESC'.
-*
-* The final argument supported is called, 'fields' and has the default value of
-* 'all'. There are multiple other options that can be used instead. Supported
-* values are as follows: 'all', 'ids', 'names', and finally
-* 'all_with_object_id'.
-*
-* The fields argument also decides what will be returned. If 'all' or
-* 'all_with_object_id' is chosen or the default kept intact, then all matching
-* terms objects will be returned. If either 'ids' or 'names' is used, then an
-* array of all matching term ids or term names will be returned respectively.
-*
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-* @uses $wpdb
+* @since 4.2.0 Added support for 'taxonomy', 'parent', and 'term_taxonomy_id' values of `$orderby`.
-*
+*              Introduced `$parent` argument.
-* @param int|array $object_ids The ID(s) of the object(s) to retrieve.
+*
+* @global wpdb $wpdb WordPress database abstraction object.
+*
+* @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 Change what is returned
+* @param array|string $args {
-* @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.
+*     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 ( (array) $taxonomies as $taxonomy ) {
+	foreach ( $taxonomies as $taxonomy ) {
 		if ( ! taxonomy_exists($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('orderby' => 'name', 'order' => 'ASC', 'fields' => 'all');
+	$defaults = array(
+		'orderby' => 'name',
+		'order'   => 'ASC',
+		'fields'  => 'all',
+		'parent'  => '',
+	);
 	$args = wp_parse_args( $args, $defaults );
 	$terms = array();
 	if ( count($taxonomies) > 1 ) {
 		foreach ( $taxonomies as $index => $taxonomy ) {
 		$t = get_taxonomy($taxonomies[0]);
 		if ( isset($t->args) && is_array($t->args) )
 			$args = array_merge($args, $t->args);
 	}
-	extract($args, EXTR_SKIP);
+	$orderby = $args['orderby'];
+	$order = $args['order'];
-	if ( 'count' == $orderby )
+	$fields = $args['fields'];
-		$orderby = 'tt.count';
-	else if ( 'name' == $orderby )
+	if ( in_array( $orderby, array( 'term_id', 'name', 'slug', 'term_group' ) ) ) {
-		$orderby = 't.name';
+		$orderby = "t.$orderby";
-	else if ( 'slug' == $orderby )
+	} else if ( in_array( $orderby, array( 'count', 'parent', 'taxonomy', 'term_taxonomy_id' ) ) ) {
-		$orderby = 't.slug';
+		$orderby = "tt.$orderby";
-	else if ( 'term_group' == $orderby )
+	} else if ( 'term_order' === $orderby ) {
-		$orderby = 't.term_group';
-	else if ( 'term_order' == $orderby )
 		$orderby = 'tr.term_order';
-	else if ( 'none' == $orderby ) {
+	} else if ( 'none' === $orderby ) {
 		$orderby = '';
 		$order = '';
 	} else {
 		$orderby = 't.term_id';
 	}
 	$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 )
+	if ( 'all' == $fields ) {
 		$select_this = 't.*, tt.*';
-	else if ( 'ids' == $fields )
+	} elseif ( 'ids' == $fields ) {
 		$select_this = 't.term_id';
-	else if ( 'names' == $fields )
+	} elseif ( 'names' == $fields ) {
 		$select_this = 't.name';
-	else if ( 'slugs' == $fields )
+	} elseif ( 'slugs' == $fields ) {
 		$select_this = 't.slug';
-	else if ( 'all_with_object_id' == $fields )
+	} elseif ( 'all_with_object_id' == $fields ) {
 		$select_this = 't.*, tt.*, tr.object_id';
+	}
-	$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 $wpdb->term_relationships AS tr ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy IN ($taxonomies) AND tr.object_id IN ($object_ids) $orderby $order";
+	$where = array(
+		"tt.taxonomy IN ($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 ) {
-		$terms = array_merge($terms, $wpdb->get_results($query));
+		$_terms = $wpdb->get_results( $query );
-		update_term_cache($terms);
+		foreach ( $_terms as $key => $term ) {
-	} else if ( 'ids' == $fields || 'names' == $fields || 'slugs' == $fields ) {
+			$_terms[$key] = sanitize_term( $term, $taxonomy, 'raw' );
-		$terms = array_merge($terms, $wpdb->get_col($query));
+		}
-	} else if ( 'tt_ids' == $fields ) {
+		$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 )
+		}
+	}
+	if ( ! $terms ) {
 		$terms = array();
+	} elseif ( $objects && 'all_with_object_id' !== $fields ) {
-	return apply_filters('wp_get_object_terms', $terms, $object_ids, $taxonomies, $args);
+		$_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.
+	 *
+	 * @since 4.2.0
+	 *
+	 * @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 $taxonomy_array  Array of taxonomies from which `$terms` were retrieved.
+	 * @param array $args            An array of arguments for retrieving terms for the given
+	 *                               object(s). See wp_get_object_terms() for details.
+	 */
+	$terms = apply_filters( 'get_object_terms', $terms, $object_id_array, $taxonomy_array, $args );
+	/**
+	 * Filter the terms for a given object or objects.
+	 *
+	 * The `$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.
+	 */
+	return apply_filters( 'wp_get_object_terms', $terms, $object_ids, $taxonomies, $args );
 }
 /**
 * Add a new term to the database.
 *
 * 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 The WordPress database object.
+* @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 string       $taxonomy The taxonomy to which to add the term.
 * @param array|string $args {
-*     Arguments to change values of the inserted term.
+*     Optional. Array or string of arguments for inserting a term.
 *
-*     @type string 'alias_of'    Slug of the term to make this term an alias of.
+*     @type string $alias_of    Slug of the term to make this term an alias of.
-*                                Default empty string. Accepts a term slug.
+*                               Default empty string. Accepts a term slug.
-*     @type string 'description' The term description.
+*     @type string $description The term description. Default empty string.
-*                                Default empty string.
+*     @type int    $parent      The id of the parent term. Default 0.
-*     @type int    'parent'      The id of the parent term.
+*     @type string $slug        The term slug to use. Default empty string.
-*                                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, WP_Error otherwise.
+* @return array|WP_Error An array containing the `term_id` and `term_taxonomy_id`,
+*                        {@see WP_Error} otherwise.
 */
 function wp_insert_term( $term, $taxonomy, $args = array() ) {
 	global $wpdb;
-	if ( ! taxonomy_exists($taxonomy) )
+	if ( ! taxonomy_exists($taxonomy) ) {
 		return new WP_Error('invalid_taxonomy', __('Invalid taxonomy'));
+	}
+	/**
+	 * Filter 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 ) )
+	if ( is_wp_error( $term ) ) {
-			return $term;
+		return $term;
+	}
-	if ( is_int($term) && 0 == $term )
+	if ( is_int($term) && 0 == $term ) {
 		return new WP_Error('invalid_term_id', __('Invalid term ID'));
+	}
-	if ( '' == trim($term) )
+	if ( '' == trim($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);
+	$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;
 	$args = sanitize_term($args, $taxonomy, 'db');
-	extract($args, EXTR_SKIP);
 	// expected_slashed ($name)
-	$name = wp_unslash($name);
+	$name = wp_unslash( $args['name'] );
-	$description = wp_unslash($description);
+	$description = wp_unslash( $args['description'] );
+	$parent = (int) $args['parent'];
-	if ( empty($slug) )
-		$slug = sanitize_title($name);
+	$slug_provided = ! empty( $args['slug'] );
+	if ( ! $slug_provided ) {
+		$slug = sanitize_title( $name );
+	} else {
+		$slug = $args['slug'];
+	}
 	$term_group = 0;
-	if ( $alias_of ) {
+	if ( $args['alias_of'] ) {
-		$alias = $wpdb->get_row( $wpdb->prepare( "SELECT term_id, term_group FROM $wpdb->terms WHERE slug = %s", $alias_of) );
+		$alias = get_term_by( 'slug', $args['alias_of'], $taxonomy );
-		if ( $alias->term_group ) {
+		if ( ! empty( $alias->term_group ) ) {
 			// The alias we want is already in a group, so let's use that one.
 			$term_group = $alias->term_group;
-		} else {
+		} elseif ( ! empty( $alias->term_id ) ) {
-			// The alias isn't in a group, so let's create a new one and firstly add the alias term to it.
+			/*
+			 * The alias is not in a group, so we create a new one
+			 * and add the alias to it.
+			 */
 			$term_group = $wpdb->get_var("SELECT MAX(term_group) FROM $wpdb->terms") + 1;
-			do_action( 'edit_terms', $alias->term_id, $taxonomy );
-			$wpdb->update($wpdb->terms, compact('term_group'), array('term_id' => $alias->term_id) );
+			wp_update_term( $alias->term_id, $taxonomy, array(
-			do_action( 'edited_terms', $alias->term_id, $taxonomy );
+				'term_group' => $term_group,
-		}
+			) );
-	}
+		}
+	}
-	if ( $term_id = term_exists($slug) ) {
-		$existing_term = $wpdb->get_row( $wpdb->prepare( "SELECT name FROM $wpdb->terms WHERE term_id = %d", $term_id), ARRAY_A );
+	/*
-		// We've got an existing term in the same taxonomy, which matches the name of the new term:
+	 * Prevent the creation of terms with duplicate names at the same level of a taxonomy hierarchy,
-		if ( is_taxonomy_hierarchical($taxonomy) && $existing_term['name'] == $name && $exists = term_exists( (int) $term_id, $taxonomy ) ) {
+	 * unless a unique slug has been explicitly provided.
-			// Hierarchical, and it matches an existing term, Do not allow same "name" in the same level.
+	 */
-			$siblings = get_terms($taxonomy, array('fields' => 'names', 'get' => 'all', 'parent' => (int)$parent) );
+	if ( $name_match = get_term_by( 'name', $name, $taxonomy ) ) {
-			if ( in_array($name, $siblings) ) {
+		$slug_match = get_term_by( 'slug', $slug, $taxonomy );
-				return new WP_Error('term_exists', __('A term with the name provided already exists with this parent.'), $exists['term_id']);
+		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' ) ) ) {
+					$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 );
+				}
 			} else {
-				$slug = wp_unique_term_slug($slug, (object) $args);
+				return new WP_Error( 'term_exists', __( 'A term with the name already exists in this taxonomy.' ), $name_match->term_id );
-				if ( false === $wpdb->insert( $wpdb->terms, compact( 'name', 'slug', 'term_group' ) ) )
-					return new WP_Error('db_insert_error', __('Could not insert term into the database'), $wpdb->last_error);
-				$term_id = (int) $wpdb->insert_id;
 			}
-		} elseif ( $existing_term['name'] != $name ) {
+		}
-			// We've got an existing term, with a different name, Create the new term.
+	}
-			$slug = wp_unique_term_slug($slug, (object) $args);
-			if ( false === $wpdb->insert( $wpdb->terms, compact( 'name', 'slug', 'term_group' ) ) )
+	$slug = wp_unique_term_slug( $slug, (object) $args );
-				return new WP_Error('db_insert_error', __('Could not insert term into the database'), $wpdb->last_error);
-			$term_id = (int) $wpdb->insert_id;
+	if ( false === $wpdb->insert( $wpdb->terms, compact( 'name', 'slug', 'term_group' ) ) ) {
-		} elseif ( $exists = term_exists( (int) $term_id, $taxonomy ) )  {
+		return new WP_Error( 'db_insert_error', __( 'Could not insert term into the database' ), $wpdb->last_error );
-			// Same name, same slug.
+	}
-			return new WP_Error('term_exists', __('A term with the name provided already exists.'), $exists['term_id']);
-		}
+	$term_id = (int) $wpdb->insert_id;
-	} else {
-		// This term does not exist at all in the database, Create it.
-		$slug = wp_unique_term_slug($slug, (object) $args);
-		if ( false === $wpdb->insert( $wpdb->terms, compact( 'name', 'slug', 'term_group' ) ) )
-			return new WP_Error('db_insert_error', __('Could not insert term into the database'), $wpdb->last_error);
-		$term_id = (int) $wpdb->insert_id;
-	}
 	// Seems unreachable, However, Is used in the case that a term name is provided, which sanitizes to an empty string.
 	if ( empty($slug) ) {
 		$slug = sanitize_title($slug, $term_id);
+		/** This action is documented in wp-includes/taxonomy.php */
 		do_action( 'edit_terms', $term_id, $taxonomy );
 		$wpdb->update( $wpdb->terms, compact( 'slug' ), compact( 'term_id' ) );
+		/** This action is documented in wp-includes/taxonomy.php */
 		do_action( 'edited_terms', $term_id, $taxonomy );
 	}
 	$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, $term_id ) );
-	if ( !empty($tt_id) )
+	if ( !empty($tt_id) ) {
 		return array('term_id' => $term_id, 'term_taxonomy_id' => $tt_id);
+	}
 	$wpdb->insert( $wpdb->term_taxonomy, compact( 'term_id', 'taxonomy', 'description', 'parent') + array( 'count' => 0 ) );
 	$tt_id = (int) $wpdb->insert_id;
-	do_action("create_term", $term_id, $tt_id, $taxonomy);
+	/*
-	do_action("create_$taxonomy", $term_id, $tt_id);
+	 * Sanity check: if we just created a term with the same parent + taxonomy + slug but a higher term_id than
+	 * an existing term, then we have unwittingly created a duplicate term. Delete the dupe, and use the term_id
-	$term_id = apply_filters('term_id_filter', $term_id, $tt_id);
+	 * and term_taxonomy_id of the older term instead. Then return out of the function so that the "create" hooks
+	 * are not fired.
+	 */
+	$duplicate_term = $wpdb->get_row( $wpdb->prepare( "SELECT t.term_id, tt.term_taxonomy_id FROM $wpdb->terms t INNER JOIN $wpdb->term_taxonomy tt ON ( tt.term_id = t.term_id ) WHERE t.slug = %s AND tt.parent = %d AND tt.taxonomy = %s AND t.term_id < %d AND tt.term_taxonomy_id != %d", $slug, $parent, $taxonomy, $term_id, $tt_id ) );
+	if ( $duplicate_term ) {
+		$wpdb->delete( $wpdb->terms, array( 'term_id' => $term_id ) );
+		$wpdb->delete( $wpdb->term_taxonomy, array( 'term_taxonomy_id' => $tt_id ) );
+		$term_id = (int) $duplicate_term->term_id;
+		$tt_id   = (int) $duplicate_term->term_taxonomy_id;
+		clean_term_cache( $term_id, $taxonomy );
+		return array( 'term_id' => $term_id, 'term_taxonomy_id' => $tt_id );
+	}
+	/**
+	 * Fires immediately after a new term is created, before the term cache is cleaned.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param int    $term_id  Term ID.
+	 * @param int    $tt_id    Term taxonomy ID.
+	 * @param string $taxonomy Taxonomy slug.
+	 */
+	do_action( "create_term", $term_id, $tt_id, $taxonomy );
+	/**
+	 * Fires after a new term is created for a specific taxonomy.
+	 *
+	 * The dynamic portion of the hook name, `$taxonomy`, refers
+	 * to the slug of the taxonomy the term was created for.
+	 *
+	 * @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 );
+	/**
+	 * Filter 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.
+	 */
+	$term_id = apply_filters( 'term_id_filter', $term_id, $tt_id );
 	clean_term_cache($term_id, $taxonomy);
-	do_action("created_term", $term_id, $tt_id, $taxonomy);
+	/**
-	do_action("created_$taxonomy", $term_id, $tt_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 );
+	/**
+	 * Fires after a new term in a specific taxonomy is created, and after the term
+	 * cache has been cleaned.
+	 *
+	 * @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 );
 	return array('term_id' => $term_id, 'term_taxonomy_id' => $tt_id);
 }
 /**
 *
 * A relationship means that the term is grouped in or belongs to the taxonomy.
 * A term has no meaning until it is given context by defining which taxonomy it
 * exists under.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-* @uses wp_remove_object_terms()
+*
-*
+* @param int              $object_id The object to relate to.
-* @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 array|int|string $terms The slug or id of the term, will replace all existing
+*                                    Will replace all existing related terms in this taxonomy.
-* related terms in this taxonomy.
+* @param string           $taxonomy  The context in which to relate the term to the object.
-* @param array|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.
-* @param bool $append If false will delete difference of terms.
+* @return array|WP_Error Affected Term IDs.
-* @return array|WP_Error Affected Term IDs
+*/
-*/
+function wp_set_object_terms( $object_id, $terms, $taxonomy, $append = false ) {
-function wp_set_object_terms($object_id, $terms, $taxonomy, $append = false) {
 	global $wpdb;
 	$object_id = (int) $object_id;
 	if ( ! taxonomy_exists($taxonomy) )
 		$tt_id = $term_info['term_taxonomy_id'];
 		$tt_ids[] = $tt_id;
 		if ( $wpdb->get_var( $wpdb->prepare( "SELECT term_taxonomy_id FROM $wpdb->term_relationships WHERE object_id = %d AND term_taxonomy_id = %d", $object_id, $tt_id ) ) )
 			continue;
+		/**
+		 * Fires immediately before an object-term relationship is added.
+		 *
+		 * @since 2.9.0
+		 *
+		 * @param int $object_id Object ID.
+		 * @param int $tt_id     Term taxonomy ID.
+		 */
 		do_action( 'add_term_relationship', $object_id, $tt_id );
 		$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
+		 *
+		 * @param int $object_id Object ID.
+		 * @param int $tt_id     Term taxonomy ID.
+		 */
 		do_action( 'added_term_relationship', $object_id, $tt_id );
 		$new_tt_ids[] = $tt_id;
 	}
 	if ( $new_tt_ids )
 				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' );
-	do_action('set_object_terms', $object_id, $terms, $tt_ids, $taxonomy, $append, $old_tt_ids);
+	/**
+	 * Fires after an object's terms have been set.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @param int    $object_id  Object ID.
+	 * @param array  $terms      An array of object terms.
+	 * @param array  $tt_ids     An array of term taxonomy IDs.
+	 * @param string $taxonomy   Taxonomy slug.
+	 * @param bool   $append     Whether to append new terms to the old terms.
+	 * @param array  $old_tt_ids Old array of term taxonomy IDs.
+	 */
+	do_action( 'set_object_terms', $object_id, $terms, $tt_ids, $taxonomy, $append, $old_tt_ids );
 	return $tt_ids;
 }
 /**
 * Add term(s) associated with a given object.
 *
-* @package WordPress
+* @since 3.6.0
-* @subpackage Taxonomy
-* @since 3.6
-* @uses wp_set_object_terms()
 *
 * @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 array|string $taxonomy Taxonomy name.
 * @return array|WP_Error Affected Term IDs
 }
 /**
 * Remove term(s) associated with a given object.
 *
-* @package WordPress
+* @since 3.6.0
-* @subpackage Taxonomy
+*
-* @since 3.6
+* @global wpdb $wpdb WordPress database abstraction object.
-* @uses $wpdb
-*
-* @uses apply_filters() Calls 'delete_term_relationships' hook with object_id and tt_ids as parameters.
-* @uses apply_filters() Calls 'deleted_term_relationships' hook with object_id and tt_ids as parameters.
 *
 * @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 array|string $taxonomy Taxonomy name.
 * @return bool|WP_Error True on success, false or WP_Error on failure.
 		$tt_ids[] = $term_info['term_taxonomy_id'];
 	}
 	if ( $tt_ids ) {
 		$in_tt_ids = "'" . implode( "', '", $tt_ids ) . "'";
+		/**
+		 * Fires immediately before an object-term relationship is deleted.
+		 *
+		 * @since 2.9.0
+		 *
+		 * @param int   $object_id Object ID.
+		 * @param array $tt_ids    An array of term taxonomy IDs.
+		 */
 		do_action( 'delete_term_relationships', $object_id, $tt_ids );
 		$deleted = $wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->term_relationships WHERE object_id = %d AND term_taxonomy_id IN ($in_tt_ids)", $object_id ) );
+		/**
+		 * Fires immediately after an object-term relationship is deleted.
+		 *
+		 * @since 2.9.0
+		 *
+		 * @param int   $object_id Object ID.
+		 * @param array $tt_ids    An array of term taxonomy IDs.
+		 */
 		do_action( 'deleted_term_relationships', $object_id, $tt_ids );
 		wp_update_term_count( $tt_ids, $taxonomy );
 		return (bool) $deleted;
 	}
 * 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.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-* @uses $wpdb
+*
+* @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param string $slug The string that will be tried for a unique slug
 * @param object $term The term object that the $slug will belong too
 * @return string Will return a true unique slug.
 */
 function wp_unique_term_slug($slug, $term) {
 	global $wpdb;
 	if ( ! term_exists( $slug ) )
 		return $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 ) ) {
+		return $slug;
+	}
 	// If the taxonomy supports hierarchy and the term has a parent, make the slug unique
 	// by incorporating parent slugs.
 	if ( is_taxonomy_hierarchical($term->taxonomy) && !empty($term->parent) ) {
 		$the_parent = $term->parent;
 * will be created for you.
 *
 * For what can be overrode in $args, check the term scheme can contain and stay
 * away from the term keys.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
 *
-* @uses $wpdb
+* @global wpdb $wpdb WordPress database abstraction object.
-* @uses do_action() Will call both 'edit_term' and 'edit_$taxonomy' twice.
-* @uses apply_filters() Will call the 'term_id_filter' filter and pass the term
-*	id and taxonomy id.
 *
 * @param int $term_id The ID of the term
 * @param string $taxonomy The context in which to relate the term to the object.
 * @param array|string $args Overwrite term field values
 * @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) )
+	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, ARRAY_A );
-	if ( is_wp_error( $term ) )
+	if ( is_wp_error( $term ) ) {
 		return $term;
+	}
+	if ( ! $term ) {
+		return new WP_Error( 'invalid_term', __( 'Empty Term' ) );
+	}
 	// Escape data pulled from DB.
 	$term = wp_slash($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' => '');
 	$args = wp_parse_args($args, $defaults);
 	$args = sanitize_term($args, $taxonomy, 'db');
-	extract($args, EXTR_SKIP);
+	$parsed_args = $args;
 	// expected_slashed ($name)
-	$name = wp_unslash($name);
+	$name = wp_unslash( $args['name'] );
-	$description = wp_unslash($description);
+	$description = wp_unslash( $args['description'] );
+	$parsed_args['name'] = $name;
+	$parsed_args['description'] = $description;
 	if ( '' == trim($name) )
 		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.' ) );
+	}
 	$empty_slug = false;
-	if ( empty($slug) ) {
+	if ( empty( $args['slug'] ) ) {
 		$empty_slug = true;
 		$slug = sanitize_title($name);
-	}
+	} else {
+		$slug = $args['slug'];
-	if ( $alias_of ) {
+	}
-		$alias = $wpdb->get_row( $wpdb->prepare( "SELECT term_id, term_group FROM $wpdb->terms WHERE slug = %s", $alias_of) );
-		if ( $alias->term_group ) {
+	$parsed_args['slug'] = $slug;
+	$term_group = isset( $parsed_args['term_group'] ) ? $parsed_args['term_group'] : 0;
+	if ( $args['alias_of'] ) {
+		$alias = get_term_by( 'slug', $args['alias_of'], $taxonomy );
+		if ( ! empty( $alias->term_group ) ) {
 			// The alias we want is already in a group, so let's use that one.
 			$term_group = $alias->term_group;
-		} else {
+		} elseif ( ! empty( $alias->term_id ) ) {
-			// The alias isn't in a group, so let's create a new one and firstly add the alias term to it.
+			/*
+			 * The alias is not in a group, so we create a new one
+			 * and add the alias to it.
+			 */
 			$term_group = $wpdb->get_var("SELECT MAX(term_group) FROM $wpdb->terms") + 1;
-			do_action( 'edit_terms', $alias->term_id, $taxonomy );
-			$wpdb->update( $wpdb->terms, compact('term_group'), array( 'term_id' => $alias->term_id ) );
+			wp_update_term( $alias->term_id, $taxonomy, array(
-			do_action( 'edited_terms', $alias->term_id, $taxonomy );
+				'term_group' => $term_group,
-		}
+			) );
-	}
+		}
-	// Check $parent to see if it will cause a hierarchy loop
+		$parsed_args['term_group'] = $term_group;
-	$parent = apply_filters( 'wp_update_term_parent', $parent, $term_id, $taxonomy, compact( array_keys( $args ) ), $args );
+	}
+	/**
+	 * Filter the term parent.
+	 *
+	 * Hook to this filter to see if it will cause a hierarchy loop.
+	 *
+	 * @since 3.1.0
+	 *
+	 * @param int    $parent      ID of the parent term.
+	 * @param int    $term_id     Term ID.
+	 * @param string $taxonomy    Taxonomy slug.
+	 * @param array  $parsed_args An array of potentially altered update arguments for the given term.
+	 * @param array  $args        An array of update arguments for the given term.
+	 */
+	$parent = apply_filters( 'wp_update_term_parent', $args['parent'], $term_id, $taxonomy, $parsed_args, $args );
 	// Check for duplicate slug
-	$id = $wpdb->get_var( $wpdb->prepare( "SELECT term_id FROM $wpdb->terms WHERE slug = %s", $slug ) );
+	$duplicate = get_term_by( 'slug', $slug, $taxonomy );
-	if ( $id && ($id != $term_id) ) {
+	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']) )
 			$slug = wp_unique_term_slug($slug, (object) $args);
 		else
 			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) );
+	// 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;
+	}
+	/**
+	 * Fires immediately before the given terms are edited.
+	 *
+	 * @since 2.9.0
+	 *
+	 * @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' ) );
 	if ( empty($slug) ) {
 		$slug = sanitize_title($name, $term_id);
 		$wpdb->update( $wpdb->terms, compact( 'slug' ), compact( 'term_id' ) );
 	}
+	/**
+	 * Fires immediately after the given terms are edited.
+	 *
+	 * @since 2.9.0
+	 *
+	 * @param int    $term_id  Term ID
+	 * @param string $taxonomy Taxonomy slug.
+	 */
 	do_action( 'edited_terms', $term_id, $taxonomy );
-	$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) );
+	/**
+	 * Fires immediate before a term-taxonomy relationship is updated.
+	 *
+	 * @since 2.9.0
+	 *
+	 * @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.
+	 *
+	 * @since 2.9.0
+	 *
+	 * @param int    $tt_id    Term taxonomy ID.
+	 * @param string $taxonomy Taxonomy slug.
+	 */
 	do_action( 'edited_term_taxonomy', $tt_id, $taxonomy );
-	do_action("edit_term", $term_id, $tt_id, $taxonomy);
+	// Clean the relationship caches for all object types using this term
-	do_action("edit_$taxonomy", $term_id, $tt_id);
+	$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 );
-	$term_id = apply_filters('term_id_filter', $term_id, $tt_id);
+	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
+	 *
+	 * @param int    $term_id  Term ID.
+	 * @param int    $tt_id    Term taxonomy ID.
+	 * @param string $taxonomy Taxonomy slug.
+	 */
+	do_action( "edit_term", $term_id, $tt_id, $taxonomy );
+	/**
+	 * Fires after a term in a specific taxonomy has been updated, but before the term
+	 * cache has been cleaned.
+	 *
+	 * The dynamic portion of the hook name, `$taxonomy`, refers to the taxonomy slug.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param int $term_id Term ID.
+	 * @param int $tt_id   Term taxonomy ID.
+	 */
+	do_action( "edit_$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);
-	do_action("edited_term", $term_id, $tt_id, $taxonomy);
+	/**
-	do_action("edited_$taxonomy", $term_id, $tt_id);
+	 * Fires after a term has been updated, and the term cache has been cleaned.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param int    $term_id  Term ID.
+	 * @param int    $tt_id    Term taxonomy ID.
+	 * @param string $taxonomy Taxonomy slug.
+	 */
+	do_action( "edited_term", $term_id, $tt_id, $taxonomy );
+	/**
+	 * Fires after a term for a specific taxonomy has been updated, and the term
+	 * cache has been cleaned.
+	 *
+	 * The dynamic portion of the hook name, `$taxonomy`, refers to the taxonomy slug.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param int $term_id Term ID.
+	 * @param int $tt_id   Term taxonomy ID.
+	 */
+	do_action( "edited_$taxonomy", $term_id, $tt_id );
 	return array('term_id' => $term_id, 'term_taxonomy_id' => $tt_id);
 }
 /**
 * the count.
 *
 * 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.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-* @uses $wpdb
+*
+* @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param int|array $terms The term_taxonomy_id of the terms
 * @param string $taxonomy The context of the term.
 * @return bool If no terms will return false, and if successful will return true.
 */
 * @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.
 */
 function wp_update_term_count_now( $terms, $taxonomy ) {
-	global $wpdb;
 	$terms = array_map('intval', $terms);
 	$taxonomy = get_taxonomy($taxonomy);
 	if ( !empty($taxonomy->update_count_callback) ) {
 		call_user_func($taxonomy->update_count_callback, $terms, $taxonomy);
 *
 * 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
 * take place.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
 *
 * @see get_object_taxonomies() for more on $object_type
-* @uses do_action() Will call action hook named, 'clean_object_term_cache' after completion.
-*	Passes, function params in same order.
 *
 * @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, $object_type) {
 	if ( !is_array($object_ids) )
 		$object_ids = array($object_ids);
 	$taxonomies = get_object_taxonomies( $object_type );
-	foreach ( $object_ids as $id )
+	foreach ( $object_ids as $id ) {
-		foreach ( $taxonomies as $taxonomy )
+		foreach ( $taxonomies as $taxonomy ) {
 			wp_cache_delete($id, "{$taxonomy}_relationships");
+		}
-	do_action('clean_object_term_cache', $object_ids, $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.
+	 */
+	do_action( 'clean_object_term_cache', $object_ids, $object_type );
 }
 /**
 * Will remove all of the term ids from the cache.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-* @uses $wpdb
+*
+* @global wpdb $wpdb WordPress database abstraction object.
 *
 * @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 bool $clean_taxonomy Whether to clean taxonomy wide caches (true), or just individual term object caches (false). Default is true.
 */
 function clean_term_cache($ids, $taxonomy = '', $clean_taxonomy = true) {
 	global $wpdb;
-	static $cleaned = array();
 	if ( !is_array($ids) )
 		$ids = array($ids);
 	$taxonomies = array();
 			}
 		}
 	}
 	foreach ( $taxonomies as $taxonomy ) {
-		if ( isset($cleaned[$taxonomy]) )
-			continue;
-		$cleaned[$taxonomy] = true;
 		if ( $clean_taxonomy ) {
 			wp_cache_delete('all_ids', $taxonomy);
 			wp_cache_delete('get', $taxonomy);
 			delete_option("{$taxonomy}_children");
 			// Regenerate {$taxonomy}_children
 			_get_term_hierarchy($taxonomy);
 		}
-		do_action('clean_term_cache', $ids, $taxonomy);
+		/**
+		 * Fires once after each taxonomy's term cache has been cleaned.
+		 *
+		 * @since 2.5.0
+		 *
+		 * @param array  $ids      An array of term IDs.
+		 * @param string $taxonomy Taxonomy slug.
+		 */
+		do_action( 'clean_term_cache', $ids, $taxonomy );
 	}
 	wp_cache_set( 'last_changed', microtime(), 'terms' );
 }
 /**
 * Retrieves the taxonomy relationship to the term object id.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
 *
-* @uses wp_cache_get() Retrieves taxonomy relationship from cache
+* @param int    $id       Term object ID
-*
-* @param int|array $id Term object ID
 * @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 $id.
 */
 function get_object_term_cache($id, $taxonomy) {
 	$cache = wp_cache_get($id, "{$taxonomy}_relationships");
 	return $cache;
 }
 /**
-* Updates the cache for Term ID(s).
+* Updates the cache for the given term object ID(s).
 *
-* Will only update the cache for terms not already cached.
+* Note: Due to performance concerns, great care should be taken to only update
-*
+* term caches when necessary. Processing time can increase exponentially depending
-* The $object_ids expects that the ids be separated by commas, if it is a
+* on both the number of passed term IDs and the number of taxonomies those terms
-* string.
+* belong to.
 *
-* It should be noted that update_object_term_cache() is very time extensive. It
+* Caches will only be updated for terms not already cached.
-* is advised that the function is not called very often or at least not for a
+*
-* lot of terms that exist in a lot of taxonomies. The amount of time increases
-* for each term and it also increases for each taxonomy the term belongs to.
-*
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
-* @uses wp_get_object_terms() Used to get terms from the database to update
+*
-*
+* @param string|array $object_ids  Comma-separated list or array of term object IDs..
-* @param string|array $object_ids Single or list of term object ID(s)
+* @param array|string $object_type The taxonomy object type.
-* @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 null|bool Null value is given with empty $object_ids. False if
+*                    `$object_ids` are already cached.
 */
 function update_object_term_cache($object_ids, $object_type) {
 	if ( empty($object_ids) )
 		return;
 	$terms = wp_get_object_terms($ids, $taxonomies, array('fields' => 'all_with_object_id'));
 	$object_terms = array();
 	foreach ( (array) $terms as $term )
-		$object_terms[$term->object_id][$term->taxonomy][$term->term_id] = $term;
+		$object_terms[$term->object_id][$term->taxonomy][] = $term;
 	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.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 2.3.0
 *
 * @param array $terms List of Term objects to change
 * @param string $taxonomy Optional. Update Term to this taxonomy in cache
 */
 	foreach ( (array) $terms as $term ) {
 		$term_taxonomy = $taxonomy;
 		if ( empty($term_taxonomy) )
 			$term_taxonomy = $term->taxonomy;
-		wp_cache_add($term->term_id, $term, $term_taxonomy);
+		wp_cache_add( $term->term_id, $term, $term_taxonomy );
 	}
 }
 //
 // Private
 //
 /**
 * Retrieves children of taxonomy as Term IDs.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @access private
 * @since 2.3.0
-*
-* @uses update_option() Stores all of the children in "$taxonomy_children"
-*	 option. That is the name of the taxonomy, immediately followed by '_children'.
 *
 * @param string $taxonomy Taxonomy Name
 * @return array Empty if $taxonomy isn't hierarchical or returns children as Term IDs.
 */
 function _get_term_hierarchy($taxonomy) {
 * 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 IDs, then _get_term_children returns an array of IDs.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @access private
 * @since 2.3.0
 *
 * @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 array  $terms     The set of terms - either an array of term objects or term IDs - from which those that
-* @param string $taxonomy The taxonomy which determines the hierarchy of the terms.
+*                          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
+*                          found terms when recursing the hierarchy. The array of located ancestors is used to prevent
+*                          infinite recursion loops. For performance, term_ids are used as array keys, with 1 as value.
 * @return array The subset of $terms that are descendants of $term_id.
 */
-function _get_term_children($term_id, $terms, $taxonomy) {
+function _get_term_children( $term_id, $terms, $taxonomy, &$ancestors = array() ) {
 	$empty_array = array();
 	if ( empty($terms) )
 		return $empty_array;
 	$term_list = array();
 	$has_children = _get_term_hierarchy($taxonomy);
 	if  ( ( 0 != $term_id ) && ! isset($has_children[$term_id]) )
 		return $empty_array;
+	// Include the term itself in the ancestors array, so we can properly detect when a loop has occurred.
+	if ( empty( $ancestors ) ) {
+		$ancestors[ $term_id ] = 1;
+	}
 	foreach ( (array) $terms as $term ) {
 		$use_id = false;
 		if ( !is_object($term) ) {
 			$term = get_term($term, $taxonomy);
 			if ( is_wp_error( $term ) )
 				return $term;
 			$use_id = true;
 		}
-		if ( $term->term_id == $term_id )
+		// Don't recurse if we've already identified the term as a child - this indicates a loop.
+		if ( isset( $ancestors[ $term->term_id ] ) ) {
 			continue;
+		}
 		if ( $term->parent == $term_id ) {
 			if ( $use_id )
 				$term_list[] = $term->term_id;
 			else
 				$term_list[] = $term;
 			if ( !isset($has_children[$term->term_id]) )
 				continue;
-			if ( $children = _get_term_children($term->term_id, $terms, $taxonomy) )
+			$ancestors[ $term->term_id ] = 1;
+			if ( $children = _get_term_children( $term->term_id, $terms, $taxonomy, $ancestors) )
 				$term_list = array_merge($term_list, $children);
 		}
 	}
 	return $term_list;
 * Add count of children to parent count.
 *
 * Recalculates term counts by including items from child terms. Assumes all
 * relevant children are already in the $terms argument.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @access private
 * @since 2.3.0
-* @uses $wpdb
+*
+* @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param array $terms List of Term IDs
 * @param string $taxonomy Term Context
 * @return null Will break from function if conditions are not met.
 */
 	if ( empty($term_hier) )
 		return;
 	$term_items = array();
+	$terms_by_id = array();
+	$term_ids = array();
 	foreach ( (array) $terms as $key => $term ) {
 		$terms_by_id[$term->term_id] = & $terms[$key];
 		$term_ids[$term->term_taxonomy_id] = $term->term_id;
 	}
 	}
 	// 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;
 			if ( !empty( $term_items[$term_id] ) )
 				foreach ( $term_items[$term_id] as $item_id => $touches ) {
 					$term_items[$parent][$item_id] = isset($term_items[$parent][$item_id]) ? ++$term_items[$parent][$item_id]: 1;
 				}
 			$child = $parent;
+			if ( in_array( $parent, $ancestors ) ) {
+				break;
+			}
 		}
 	}
 	// Transfer the touched cells
 	foreach ( (array) $term_items as $id => $items )
 * Will update term count based on object types of the current taxonomy.
 *
 * Private function for the default callback for post_tag and category
 * taxonomies.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @access private
 * @since 2.3.0
-* @uses $wpdb
+*
+* @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param array $terms List of Term taxonomy IDs
 * @param object $taxonomy Current taxonomy object of terms
 */
 function _update_post_term_count( $terms, $taxonomy ) {
 			$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 ) );
-		do_action( 'edit_term_taxonomy', $term, $taxonomy );
+		/** This action is documented in wp-includes/taxonomy.php */
+		do_action( 'edit_term_taxonomy', $term, $taxonomy->name );
 		$wpdb->update( $wpdb->term_taxonomy, compact( 'count' ), array( 'term_taxonomy_id' => $term ) );
-		do_action( 'edited_term_taxonomy', $term, $taxonomy );
+		/** This action is documented in wp-includes/taxonomy.php */
+		do_action( 'edited_term_taxonomy', $term, $taxonomy->name );
 	}
 }
 /**
 * Will update term count based on number of objects.
 *
 * Default callback for the link_category taxonomy.
 *
-* @package WordPress
-* @subpackage Taxonomy
 * @since 3.3.0
-* @uses $wpdb
+*
+* @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param array $terms List of Term taxonomy IDs
 * @param object $taxonomy Current taxonomy object of terms
 */
 function _update_generic_term_count( $terms, $taxonomy ) {
 	global $wpdb;
 	foreach ( (array) $terms as $term ) {
 		$count = $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM $wpdb->term_relationships WHERE term_taxonomy_id = %d", $term ) );
-		do_action( 'edit_term_taxonomy', $term, $taxonomy );
+		/** This action is documented in wp-includes/taxonomy.php */
+		do_action( 'edit_term_taxonomy', $term, $taxonomy->name );
 		$wpdb->update( $wpdb->term_taxonomy, compact( 'count' ), array( 'term_taxonomy_id' => $term ) );
-		do_action( 'edited_term_taxonomy', $term, $taxonomy );
-	}
+		/** This action is documented in wp-includes/taxonomy.php */
-}
+		do_action( 'edited_term_taxonomy', $term, $taxonomy->name );
+	}
-/**
+}
-* Generates a permalink for a taxonomy term archive.
+/**
+* Create a new term for a term_taxonomy item that currently shares its term with another term_taxonomy.
+*
+* @ignore
+* @since 4.2.0
+*
+* @param int  $term_id          ID of the shared term.
+* @param int  $term_taxonomy_id ID of the term_taxonomy item to receive a new term.
+* @return int|WP_Error When the current term does not need to be split (or cannot be split on the current
+*                      database schema), `$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 ) {
+	global $wpdb;
+	// Don't try to split terms if database schema does not support shared slugs.
+	$current_db_version = get_option( 'db_version' );
+	if ( $current_db_version < 30133 ) {
+		return $term_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;
+	}
+	// 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 ) );
+	$new_term_data = array(
+		'name' => $shared_term->name,
+		'slug' => $shared_term->slug,
+		'term_group' => $shared_term->term_group,
+	);
+	if ( false === $wpdb->insert( $wpdb->terms, $new_term_data ) ) {
+		return new WP_Error( 'db_insert_error', __( 'Could not split shared term.' ), $wpdb->last_error );
+	}
+	$new_term_id = (int) $wpdb->insert_id;
+	// Update the existing term_taxonomy to point to the newly created term.
+	$wpdb->update( $wpdb->term_taxonomy,
+		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 ) );
+	$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 ) );
+	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 );
+		}
+	} 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 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 ) );
+	if ( $shared_term_taxonomies ) {
+		foreach ( $shared_term_taxonomies as $shared_term_taxonomy ) {
+			clean_term_cache( $term_id, $shared_term_taxonomy );
+		}
+	}
+	// Keep a record of term_ids that have been split, keyed by old term_id. See {@see wp_get_split_term()}.
+	$split_term_data = get_option( '_split_terms', 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;
+	update_option( '_split_terms', $split_term_data );
+	/**
+	 * Fires after a previously shared taxonomy term is split into two separate terms.
+	 *
+	 * @since 4.2.0
+	 *
+	 * @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.
+	 */
+	do_action( 'split_shared_term', $term_id, $new_term_id, $term_taxonomy_id, $term_taxonomy->taxonomy );
+	return $new_term_id;
+}
+/**
+* Check default categories when a term gets split to see if any of them need to be updated.
+*
+* @ignore
+* @since 4.2.0
+*
+* @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_default_terms( $term_id, $new_term_id, $term_taxonomy_id, $taxonomy ) {
+	if ( 'category' != $taxonomy ) {
+		return;
+	}
+	foreach ( array( 'default_category', 'default_link_category', 'default_email_category' ) as $option ) {
+		if ( $term_id == get_option( $option, -1 ) ) {
+			update_option( $option, $new_term_id );
+		}
+	}
+}
+/**
+* Check menu items when a term gets split to see if any of them need to be updated.
+*
+* @ignore
+* @since 4.2.0
+*
+* @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_terms_in_menus( $term_id, $new_term_id, $term_taxonomy_id, $taxonomy ) {
+	global $wpdb;
+	$post_ids = $wpdb->get_col( $wpdb->prepare(
+		"SELECT m1.post_id
+		FROM {$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 ( m3.meta_key = '_menu_item_object_id' AND m3.meta_value = %d )",
+		$taxonomy,
+		$term_id
+	) );
+	if ( $post_ids ) {
+		foreach ( $post_ids as $post_id ) {
+			update_post_meta( $post_id, '_menu_item_object_id', $new_term_id, $term_id );
+		}
+	}
+}
+/**
+* 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.
+* @return array Array of new term IDs, keyed by taxonomy.
+*/
+function wp_get_split_terms( $old_term_id ) {
+	$split_terms = get_option( '_split_terms', array() );
+	$terms = array();
+	if ( isset( $split_terms[ $old_term_id ] ) ) {
+		$terms = $split_terms[ $old_term_id ];
+	}
+	return $terms;
+}
+/**
+* Get the new term ID corresponding to a previously split term.
+*
+* @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,
+*                  the new term_id will be returned. If no previously split term is found matching
+*                  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;
+	if ( isset( $split_terms[ $taxonomy ] ) ) {
+		$term_id = (int) $split_terms[ $taxonomy ];
+	}
+	return $term_id;
+}
+/**
+* Generate a permalink for a taxonomy term archive.
 *
 * @since 2.5.0
 *
-* @uses apply_filters() Calls 'term_link' with term link and term object, and taxonomy parameters.
+* @param object|int|string $term     The term object, ID, or slug whose link will be retrieved.
-* @uses apply_filters() For the post_tag Taxonomy, Calls 'tag_link' with tag link and tag ID as parameters.
+* @param string            $taxonomy Optional. Taxonomy. Default empty.
-* @uses apply_filters() For the category Taxonomy, Calls 'category_link' filter on category link and category ID.
-*
-* @param object|int|string $term
-* @param string $taxonomy (optional if $term is object)
 * @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 = '') {
 	global $wp_rewrite;
 			$termlink = "?taxonomy=$taxonomy&term=$slug";
 		$termlink = home_url($termlink);
 	} else {
 		if ( $t->rewrite['hierarchical'] ) {
 			$hierarchical_slugs = array();
-			$ancestors = get_ancestors($term->term_id, $taxonomy);
+			$ancestors = get_ancestors( $term->term_id, $taxonomy, 'taxonomy' );
 			foreach ( (array)$ancestors as $ancestor ) {
 				$ancestor_term = get_term($ancestor, $taxonomy);
 				$hierarchical_slugs[] = $ancestor_term->slug;
 			}
 			$hierarchical_slugs = array_reverse($hierarchical_slugs);
 			$termlink = str_replace("%$taxonomy%", $slug, $termlink);
 		}
 		$termlink = home_url( user_trailingslashit($termlink, 'category') );
 	}
 	// Back Compat filters.
-	if ( 'post_tag' == $taxonomy )
+	if ( 'post_tag' == $taxonomy ) {
+		/**
+		 * Filter the tag link.
+		 *
+		 * @since 2.3.0
+		 * @deprecated 2.5.0 Use 'term_link' instead.
+		 *
+		 * @param string $termlink Tag link URL.
+		 * @param int    $term_id  Term ID.
+		 */
 		$termlink = apply_filters( 'tag_link', $termlink, $term->term_id );
-	elseif ( 'category' == $taxonomy )
+	} elseif ( 'category' == $taxonomy ) {
+		/**
+		 * Filter the category link.
+		 *
+		 * @since 1.5.0
+		 * @deprecated 2.5.0 Use 'term_link' instead.
+		 *
+		 * @param string $termlink Category link URL.
+		 * @param int    $term_id  Term ID.
+		 */
 		$termlink = apply_filters( 'category_link', $termlink, $term->term_id );
+	}
-	return apply_filters('term_link', $termlink, $term, $taxonomy);
+	/**
+	 * Filter the term link.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param string $termlink Term link URL.
+	 * @param object $term     Term object.
+	 * @param string $taxonomy Taxonomy slug.
+	 */
+	return apply_filters( 'term_link', $termlink, $term, $taxonomy );
 }
 /**
 * Display the taxonomies of a post with available options.
 *
 * This function can be used within the loop to display the taxonomies for a
 * post without specifying the Post ID. You can also use it outside the Loop to
 * display the taxonomies for a specific post.
 *
-* The available defaults are:
-* 'post' : default is 0. The post ID to get taxonomies of.
-* 'before' : default is empty string. Display before taxonomies list.
-* 'sep' : default is empty string. Separate every taxonomy with value in this.
-* 'after' : default is empty string. Display this after the taxonomies list.
-* 'template' : The template to use for displaying the taxonomy terms.
-*
 * @since 2.5.0
-* @uses get_the_taxonomies()
+*
-*
+* @param array $args {
-* @param array $args Override the defaults.
+*     Arguments about which post to use and how to format the output. Shares all of the arguments supported by
-*/
+*     {@link get_the_taxonomies()}, in addition to the following.
-function the_taxonomies($args = array()) {
+*
+*     @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' => '',
 		'sep' => ' ',
 		'after' => '',
-		'template' => '%s: %l.'
 	);
 	$r = wp_parse_args( $args, $defaults );
-	extract( $r, EXTR_SKIP );
+	echo $r['before'] . join( $r['sep'], get_the_taxonomies( $r['post'], $r ) ) . $r['after'];
-	echo $before . join($sep, get_the_taxonomies($post, $r)) . $after;
 }
 /**
 * Retrieve all taxonomies associated with a post.
 *
 * This function can be used within the loop. It will also return an array of
 * the taxonomies with links to the taxonomy and name.
 *
 * @since 2.5.0
 *
-* @param int $post Optional. Post ID or will use Global Post ID (in loop).
+* @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global $post.
-* @param array $args Override the defaults.
+* @param array $args {
+*     Arguments about how to format the list of taxonomies.
+*
+*     @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.
+* }
+* @return array List of taxonomies.
+*/
+function get_the_taxonomies( $post = 0, $args = array() ) {
+	$post = get_post( $post );
+	$args = wp_parse_args( $args, array(
+		/* translators: %s: taxonomy label, %l: list of terms formatted as per $term_template */
+		'template' => __( '%s: %l.' ),
+		'term_template' => '<a href="%1$s">%2$s</a>',
+	) );
+	$taxonomies = array();
+	if ( ! $post ) {
+		return $taxonomies;
+	}
+	foreach ( get_object_taxonomies( $post ) as $taxonomy ) {
+		$t = (array) get_taxonomy( $taxonomy );
+		if ( empty( $t['label'] ) ) {
+			$t['label'] = $taxonomy;
+		}
+		if ( empty( $t['args'] ) ) {
+			$t['args'] = array();
+		}
+		if ( empty( $t['template'] ) ) {
+			$t['template'] = $args['template'];
+		}
+		if ( empty( $t['term_template'] ) ) {
+			$t['term_template'] = $args['term_template'];
+		}
+		$terms = get_object_term_cache( $post->ID, $taxonomy );
+		if ( false === $terms ) {
+			$terms = wp_get_object_terms( $post->ID, $taxonomy, $t['args'] );
+		}
+		$links = array();
+		foreach ( $terms as $term ) {
+			$links[] = wp_sprintf( $t['term_template'], esc_attr( get_term_link( $term ) ), $term->name );
+		}
+		if ( $links ) {
+			$taxonomies[$taxonomy] = wp_sprintf( $t['template'], $t['label'], $links, $terms );
+		}
+	}
+	return $taxonomies;
+}
+/**
+* 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 $post.
 * @return array
 */
-function get_the_taxonomies($post = 0, $args = array() ) {
+function get_post_taxonomies( $post = 0 ) {
-	$post = get_post( $post );
-	$args = wp_parse_args( $args, array(
-		'template' => '%s: %l.',
-	) );
-	extract( $args, EXTR_SKIP );
-	$taxonomies = array();
-	if ( !$post )
-		return $taxonomies;
-	foreach ( get_object_taxonomies($post) as $taxonomy ) {
-		$t = (array) get_taxonomy($taxonomy);
-		if ( empty($t['label']) )
-			$t['label'] = $taxonomy;
-		if ( empty($t['args']) )
-			$t['args'] = array();
-		if ( empty($t['template']) )
-			$t['template'] = $template;
-		$terms = get_object_term_cache($post->ID, $taxonomy);
-		if ( false === $terms )
-			$terms = wp_get_object_terms($post->ID, $taxonomy, $t['args']);
-		$links = array();
-		foreach ( $terms as $term )
-			$links[] = "<a href='" . esc_attr( get_term_link($term) ) . "'>$term->name</a>";
-		if ( $links )
-			$taxonomies[$taxonomy] = wp_sprintf($t['template'], $t['label'], $links, $terms);
-	}
-	return $taxonomies;
-}
-/**
-* Retrieve all taxonomies of a post with just the names.
-*
-* @since 2.5.0
-* @uses get_object_taxonomies()
-*
-* @param int $post Optional. Post ID
-* @return array
-*/
-function get_post_taxonomies($post = 0) {
 	$post = get_post( $post );
 	return get_object_taxonomies($post);
 }
 * The given terms are checked against the object's terms' term_ids, names and slugs.
 * 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
-* @uses get_object_term_cache()
-* @uses wp_get_object_terms()
 *
 * @param int $object_id ID of the object (post ID, link ID, ...)
 * @param string $taxonomy Single taxonomy name
 * @param int|string|array $terms Optional. Term term_id, name, slug or array of said
-* @return bool|WP_Error. WP_Error on input error.
+* @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' ) );
 		$strs = array_diff( $terms, $ints );
 	else
 		$strs =& $terms;
 	foreach ( $object_terms as $object_term ) {
-		if ( $ints && in_array( $object_term->term_id, $ints ) ) return true; // If int, check against term_id
+		// If term is an int, check against term_ids only.
+		if ( $ints && in_array( $object_term->term_id, $ints ) ) {
+			return true;
+		}
 		if ( $strs ) {
-			if ( in_array( $object_term->term_id, $strs ) ) return true;
+			// Only check numeric strings against term_id, to avoid false matches due to type juggling.
-			if ( in_array( $object_term->name, $strs ) )    return true;
+			$numeric_strs = array_map( 'intval', array_filter( $strs, 'is_numeric' ) );
-			if ( in_array( $object_term->slug, $strs ) )    return true;
+			if ( in_array( $object_term->term_id, $numeric_strs, true ) ) {
+				return true;
+			}
+			if ( in_array( $object_term->name, $strs ) ) return true;
+			if ( in_array( $object_term->slug, $strs ) ) return true;
 		}
 	}
 	return false;
 }
 /**
 * Determine if the given object type is associated with the given taxonomy.
 *
 * @since 3.0.0
-* @uses get_object_taxonomies()
 *
 * @param string $object_type Object type string
 * @param string $taxonomy Single taxonomy name
 * @return bool True if object is associated with the taxonomy, otherwise false.
 */
 }
 /**
 * Get an array of ancestor IDs for a given object.
 *
-* @param int $object_id The ID of the object
+* @since 3.1.0
-* @param string $object_type The type of object for which we'll be retrieving ancestors.
+* @since 4.1.0 Introduced the `$resource_type` argument.
-* @return array of ancestors from lowest to highest in the hierarchy.
+*
-*/
+* @param int    $object_id     Optional. The ID of the object. Default 0.
-function get_ancestors($object_id = 0, $object_type = '') {
+* @param string $object_type   Optional. The type of object for which we'll be retrieving
+*                              ancestors. Accepts a post type or a taxonomy name. Default empty.
+* @param string $resource_type Optional. Type of resource $object_type is. Accepts 'post_type'
+*                              or 'taxonomy'. Default empty.
+* @return array An array of ancestors from lowest to highest in the hierarchy.
+*/
+function get_ancestors( $object_id = 0, $object_type = '', $resource_type = '' ) {
 	$object_id = (int) $object_id;
 	$ancestors = array();
 	if ( empty( $object_id ) ) {
-		return apply_filters('get_ancestors', $ancestors, $object_id, $object_type);
-	}
+		/** This filter is documented in wp-includes/taxonomy.php */
+		return apply_filters( 'get_ancestors', $ancestors, $object_id, $object_type, $resource_type );
-	if ( is_taxonomy_hierarchical( $object_type ) ) {
+	}
+	if ( ! $resource_type ) {
+		if ( is_taxonomy_hierarchical( $object_type ) ) {
+			$resource_type = 'taxonomy';
+		} elseif ( post_type_exists( $object_type ) ) {
+			$resource_type = 'post_type';
+		}
+	}
+	if ( 'taxonomy' === $resource_type ) {
 		$term = get_term($object_id, $object_type);
 		while ( ! is_wp_error($term) && ! empty( $term->parent ) && ! in_array( $term->parent, $ancestors ) ) {
 			$ancestors[] = (int) $term->parent;
 			$term = get_term($term->parent, $object_type);
 		}
-	} elseif ( post_type_exists( $object_type ) ) {
+	} elseif ( 'post_type' === $resource_type ) {
 		$ancestors = get_post_ancestors($object_id);
 	}
-	return apply_filters('get_ancestors', $ancestors, $object_id, $object_type);
+	/**
+	 * Filter a given object's ancestors.
+	 *
+	 * @since 3.1.0
+	 * @since 4.1.0 Introduced the `$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
 *
 * Prevents loops from forming and breaks those that it finds.
 *
 * Attached to the wp_update_term_parent filter.
 *
 * @since 3.1.0
-* @uses wp_find_hierarchy_loop()
 *
 * @param int $parent term_id of the parent for 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.
 *

changeset 5	5e2f62d02dcd
parent 0	d970ebf37754
child 7	cf61fcea0001