wp/wp-includes/class-wp-term-query.php
changeset 7 cf61fcea0001
child 9 177826044cd9
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/class-wp-term-query.php	Mon Oct 14 17:39:30 2019 +0200
@@ -0,0 +1,996 @@
+<?php
+
+/**
+ * Taxonomy API: WP_Term_Query class.
+ *
+ * @package WordPress
+ * @subpackage Taxonomy
+ * @since 4.6.0
+ */
+
+/**
+ * Class used for querying terms.
+ *
+ * @since 4.6.0
+ *
+ * @see WP_Term_Query::__construct() for accepted arguments.
+ */
+class WP_Term_Query {
+
+	/**
+	 * SQL string used to perform database query.
+	 *
+	 * @since 4.6.0
+	 * @var string
+	 */
+	public $request;
+
+	/**
+	 * Metadata query container.
+	 *
+	 * @since 4.6.0
+	 * @var object WP_Meta_Query
+	 */
+	public $meta_query = false;
+
+	/**
+	 * Metadata query clauses.
+	 *
+	 * @since 4.6.0
+	 * @var array
+	 */
+	protected $meta_query_clauses;
+
+	/**
+	 * SQL query clauses.
+	 *
+	 * @since 4.6.0
+	 * @var array
+	 */
+	protected $sql_clauses = array(
+		'select'  => '',
+		'from'    => '',
+		'where'   => array(),
+		'orderby' => '',
+		'limits'  => '',
+	);
+
+	/**
+	 * Query vars set by the user.
+	 *
+	 * @since 4.6.0
+	 * @var array
+	 */
+	public $query_vars;
+
+	/**
+	 * Default values for query vars.
+	 *
+	 * @since 4.6.0
+	 * @var array
+	 */
+	public $query_var_defaults;
+
+	/**
+	 * List of terms located by the query.
+	 *
+	 * @since 4.6.0
+	 * @var array
+	 */
+	public $terms;
+
+	/**
+	 * Constructor.
+	 *
+	 * Sets up the term query, based on the query vars passed.
+	 *
+	 * @since 4.6.0
+	 * @since 4.6.0 Introduced 'term_taxonomy_id' parameter.
+	 * @since 4.7.0 Introduced 'object_ids' parameter.
+	 * @since 4.9.0 Added 'slug__in' support for 'orderby'.
+	 *
+	 * @param string|array $query {
+	 *     Optional. Array or query string of term query parameters. Default empty.
+	 *
+	 *     @type string|array $taxonomy               Taxonomy name, or array of taxonomies, to which results should
+	 *                                                be limited.
+	 *     @type int|array    $object_ids             Optional. Object ID, or array of object IDs. Results will be
+	 *                                                limited to terms associated with these objects.
+	 *     @type string       $orderby                Field(s) to order terms by. Accepts term fields ('name',
+	 *                                                'slug', 'term_group', 'term_id', 'id', 'description', 'parent'),
+	 *                                                'count' for term taxonomy count, 'include' to match the
+	 *                                                'order' of the $include param, 'slug__in' to match the
+	 *                                                'order' of the $slug param, 'meta_value', 'meta_value_num',
+	 *                                                the value of `$meta_key`, the array keys of `$meta_query`, or
+	 *                                                'none' to omit the ORDER BY clause. 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). Note that $number may
+	 *                                                not return accurate results when coupled with $object_ids.
+	 *                                                See #41796 for details.
+	 *     @type int          $offset                 The number by which to offset the terms query. Default empty.
+	 *     @type string       $fields                 Term fields to query for. Accepts 'all' (returns an array of
+	 *                                                complete term objects), 'all_with_object_id' (returns an
+	 *                                                array of term objects with the 'object_id' param; only works
+	 *                                                when the `$fields` parameter is 'object_ids' ), 'ids'
+	 *                                                (returns an array of ids), 'tt_ids' (returns an array of
+	 *                                                term taxonomy ids), 'id=>parent' (returns an associative
+	 *                                                array with ids as keys, parent term IDs as values), 'names'
+	 *                                                (returns an array of term names), 'count' (returns the number
+	 *                                                of matching terms), 'id=>name' (returns an associative array
+	 *                                                with ids as keys, term names as values), or 'id=>slug'
+	 *                                                (returns an associative array with ids as keys, term slugs
+	 *                                                as values). Default 'all'.
+	 *     @type bool         $count                  Whether to return a term count (true) or array of term objects
+	 *                                                (false). Will take precedence over `$fields` if true.
+	 *                                                Default false.
+	 *     @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 int|array    $term_taxonomy_id       Optional. Term taxonomy ID, or array of term taxonomy IDs,
+	 *                                                to match when querying terms.
+	 *     @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'.
+	 *     @type bool         $update_term_meta_cache Whether to prime meta caches for matched terms. Default true.
+	 *     @type array        $meta_query             Optional. Meta query clauses to limit retrieved terms by.
+	 *                                                See `WP_Meta_Query`. Default empty.
+	 *     @type string       $meta_key               Limit terms to those matching a specific metadata key.
+	 *                                                Can be used in conjunction with `$meta_value`. Default empty.
+	 *     @type string       $meta_value             Limit terms to those matching a specific metadata value.
+	 *                                                Usually used in conjunction with `$meta_key`. Default empty.
+	 *     @type string       $meta_type              Type of object metadata is for (e.g., comment, post, or user).
+	 *                                                Default empty.
+	 *     @type string       $meta_compare           Comparison operator to test the 'meta_value'. Default empty.
+	 * }
+	 */
+	public function __construct( $query = '' ) {
+		$this->query_var_defaults = array(
+			'taxonomy'               => null,
+			'object_ids'             => null,
+			'orderby'                => 'name',
+			'order'                  => 'ASC',
+			'hide_empty'             => true,
+			'include'                => array(),
+			'exclude'                => array(),
+			'exclude_tree'           => array(),
+			'number'                 => '',
+			'offset'                 => '',
+			'fields'                 => 'all',
+			'count'                  => false,
+			'name'                   => '',
+			'slug'                   => '',
+			'term_taxonomy_id'       => '',
+			'hierarchical'           => true,
+			'search'                 => '',
+			'name__like'             => '',
+			'description__like'      => '',
+			'pad_counts'             => false,
+			'get'                    => '',
+			'child_of'               => 0,
+			'parent'                 => '',
+			'childless'              => false,
+			'cache_domain'           => 'core',
+			'update_term_meta_cache' => true,
+			'meta_query'             => '',
+			'meta_key'               => '',
+			'meta_value'             => '',
+			'meta_type'              => '',
+			'meta_compare'           => '',
+		);
+
+		if ( ! empty( $query ) ) {
+			$this->query( $query );
+		}
+	}
+
+	/**
+	 * Parse arguments passed to the term query with default query parameters.
+	 *
+	 * @since 4.6.0
+	 *
+	 * @param string|array $query WP_Term_Query arguments. See WP_Term_Query::__construct()
+	 */
+	public function parse_query( $query = '' ) {
+		if ( empty( $query ) ) {
+			$query = $this->query_vars;
+		}
+
+		$taxonomies = isset( $query['taxonomy'] ) ? (array) $query['taxonomy'] : null;
+
+		/**
+		 * Filters the terms query default arguments.
+		 *
+		 * Use {@see 'get_terms_args'} to filter the passed arguments.
+		 *
+		 * @since 4.4.0
+		 *
+		 * @param array $defaults   An array of default get_terms() arguments.
+		 * @param array $taxonomies An array of taxonomies.
+		 */
+		$this->query_var_defaults = apply_filters( 'get_terms_defaults', $this->query_var_defaults, $taxonomies );
+
+		$query = wp_parse_args( $query, $this->query_var_defaults );
+
+		$query['number'] = absint( $query['number'] );
+		$query['offset'] = absint( $query['offset'] );
+
+		// 'parent' overrides 'child_of'.
+		if ( 0 < intval( $query['parent'] ) ) {
+			$query['child_of'] = false;
+		}
+
+		if ( 'all' == $query['get'] ) {
+			$query['childless'] = false;
+			$query['child_of'] = 0;
+			$query['hide_empty'] = 0;
+			$query['hierarchical'] = false;
+			$query['pad_counts'] = false;
+		}
+
+		$query['taxonomy'] = $taxonomies;
+
+		$this->query_vars = $query;
+
+		/**
+		 * Fires after term query vars have been parsed.
+		 *
+		 * @since 4.6.0
+		 *
+		 * @param WP_Term_Query $this Current instance of WP_Term_Query.
+		 */
+		do_action( 'parse_term_query', $this );
+	}
+
+	/**
+	 * Sets up the query for retrieving terms.
+	 *
+	 * @since 4.6.0
+	 *
+	 * @param string|array $query Array or URL query string of parameters.
+	 * @return array|int List of terms, or number of terms when 'count' is passed as a query var.
+	 */
+	public function query( $query ) {
+		$this->query_vars = wp_parse_args( $query );
+		return $this->get_terms();
+	}
+
+	/**
+	 * Get terms, based on query_vars.
+	 *
+	 * @since 4.6.0
+	 *
+	 * @global wpdb $wpdb WordPress database abstraction object.
+	 *
+	 * @return array List of terms.
+	 */
+	public function get_terms() {
+		global $wpdb;
+
+		$this->parse_query( $this->query_vars );
+		$args = &$this->query_vars;
+
+		// Set up meta_query so it's available to 'pre_get_terms'.
+		$this->meta_query = new WP_Meta_Query();
+		$this->meta_query->parse_query_vars( $args );
+
+		/**
+		 * Fires before terms are retrieved.
+		 *
+		 * @since 4.6.0
+		 *
+		 * @param WP_Term_Query $this Current instance of WP_Term_Query.
+		 */
+		do_action( 'pre_get_terms', $this );
+
+		$taxonomies = (array) $args['taxonomy'];
+
+		// Save queries by not crawling the tree in the case of multiple taxes or a flat tax.
+		$has_hierarchical_tax = false;
+		if ( $taxonomies ) {
+			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;
+		}
+
+		/**
+		 * Filters the terms query arguments.
+		 *
+		 * @since 3.1.0
+		 *
+		 * @param array $args       An array of get_terms() arguments.
+		 * @param array $taxonomies An array of taxonomies.
+		 */
+		$args = apply_filters( 'get_terms_args', $args, $taxonomies );
+
+		// Avoid the query if the queried parent/child_of term has no descendants.
+		$child_of = $args['child_of'];
+		$parent   = $args['parent'];
+
+		if ( $child_of ) {
+			$_parent = $child_of;
+		} elseif ( $parent ) {
+			$_parent = $parent;
+		} else {
+			$_parent = false;
+		}
+
+		if ( $_parent ) {
+			$in_hierarchy = false;
+			foreach ( $taxonomies as $_tax ) {
+				$hierarchy = _get_term_hierarchy( $_tax );
+
+				if ( isset( $hierarchy[ $_parent ] ) ) {
+					$in_hierarchy = true;
+				}
+			}
+
+			if ( ! $in_hierarchy ) {
+				return array();
+			}
+		}
+
+		// 'term_order' is a legal sort order only when joining the relationship table.
+		$_orderby = $this->query_vars['orderby'];
+		if ( 'term_order' === $_orderby && empty( $this->query_vars['object_ids'] ) ) {
+			$_orderby = 'term_id';
+		}
+		$orderby = $this->parse_orderby( $_orderby );
+
+		if ( $orderby ) {
+			$orderby = "ORDER BY $orderby";
+		}
+
+		$order = $this->parse_order( $this->query_vars['order'] );
+
+		if ( $taxonomies ) {
+			$this->sql_clauses['where']['taxonomy'] = "tt.taxonomy IN ('" . implode( "', '", array_map( 'esc_sql', $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 ) ) {
+			$this->sql_clauses['where']['inclusions'] = 't.term_id IN ( ' . $inclusions . ' )';
+		}
+
+		$exclusions = array();
+		if ( ! empty( $exclude_tree ) ) {
+			$exclude_tree = wp_parse_id_list( $exclude_tree );
+			$excluded_children = $exclude_tree;
+			foreach ( $exclude_tree as $extrunk ) {
+				$excluded_children = array_merge(
+					$excluded_children,
+					(array) get_terms( reset( $taxonomies ), array(
+						'child_of' => intval( $extrunk ),
+						'fields' => 'ids',
+						'hide_empty' => 0
+					) )
+				);
+			}
+			$exclusions = array_merge( $excluded_children, $exclusions );
+		}
+
+		if ( ! empty( $exclude ) ) {
+			$exclusions = array_merge( wp_parse_id_list( $exclude ), $exclusions );
+		}
+
+		// 'childless' terms are those without an entry in the flattened term hierarchy.
+		$childless = (bool) $args['childless'];
+		if ( $childless ) {
+			foreach ( $taxonomies as $_tax ) {
+				$term_hierarchy = _get_term_hierarchy( $_tax );
+				$exclusions = array_merge( array_keys( $term_hierarchy ), $exclusions );
+			}
+		}
+
+		if ( ! empty( $exclusions ) ) {
+			$exclusions = 't.term_id NOT IN (' . implode( ',', array_map( 'intval', $exclusions ) ) . ')';
+		} else {
+			$exclusions = '';
+		}
+
+		/**
+		 * Filters 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 ) ) {
+			// Must do string manipulation here for backward compatibility with filter.
+			$this->sql_clauses['where']['exclusions'] = preg_replace( '/^\s*AND\s*/', '', $exclusions );
+		}
+
+		if (
+			( ! empty( $args['name'] ) ) ||
+			( is_string( $args['name'] ) && 0 !== strlen( $args['name'] ) )
+		) {
+			$names = (array) $args['name'];
+			foreach ( $names as &$_name ) {
+				// `sanitize_term_field()` returns slashed data.
+				$_name = stripslashes( sanitize_term_field( 'name', $_name, 0, reset( $taxonomies ), 'db' ) );
+			}
+
+			$this->sql_clauses['where']['name'] = "t.name IN ('" . implode( "', '", array_map( 'esc_sql', $names ) ) . "')";
+		}
+
+		if (
+			( ! empty( $args['slug'] ) ) ||
+			( is_string( $args['slug'] ) && 0 !== strlen( $args['slug'] ) )
+		) {
+			if ( is_array( $args['slug'] ) ) {
+				$slug = array_map( 'sanitize_title', $args['slug'] );
+				$this->sql_clauses['where']['slug'] = "t.slug IN ('" . implode( "', '", $slug ) . "')";
+			} else {
+				$slug = sanitize_title( $args['slug'] );
+				$this->sql_clauses['where']['slug'] = "t.slug = '$slug'";
+			}
+		}
+
+		if ( ! empty( $args['term_taxonomy_id'] ) ) {
+			if ( is_array( $args['term_taxonomy_id'] ) ) {
+				$tt_ids = implode( ',', array_map( 'intval', $args['term_taxonomy_id'] ) );
+				$this->sql_clauses['where']['term_taxonomy_id'] = "tt.term_taxonomy_id IN ({$tt_ids})";
+			} else {
+				$this->sql_clauses['where']['term_taxonomy_id'] = $wpdb->prepare( "tt.term_taxonomy_id = %d", $args['term_taxonomy_id'] );
+			}
+		}
+
+		if ( ! empty( $args['name__like'] ) ) {
+			$this->sql_clauses['where']['name__like'] = $wpdb->prepare( "t.name LIKE %s", '%' . $wpdb->esc_like( $args['name__like'] ) . '%' );
+		}
+
+		if ( ! empty( $args['description__like'] ) ) {
+			$this->sql_clauses['where']['description__like'] = $wpdb->prepare( "tt.description LIKE %s", '%' . $wpdb->esc_like( $args['description__like'] ) . '%' );
+		}
+
+		if ( ! empty( $args['object_ids'] ) ) {
+			$object_ids = $args['object_ids'];
+			if ( ! is_array( $object_ids ) ) {
+				$object_ids = array( $object_ids );
+			}
+
+			$object_ids = implode( ', ', array_map( 'intval', $object_ids ) );
+			$this->sql_clauses['where']['object_ids'] = "tr.object_id IN ($object_ids)";
+		}
+
+		/*
+		 * When querying for object relationships, the 'count > 0' check
+		 * added by 'hide_empty' is superfluous.
+		 */
+		if ( ! empty( $args['object_ids'] ) ) {
+			$args['hide_empty'] = false;
+		}
+
+		if ( '' !== $parent ) {
+			$parent = (int) $parent;
+			$this->sql_clauses['where']['parent'] = "tt.parent = '$parent'";
+		}
+
+		$hierarchical = $args['hierarchical'];
+		if ( 'count' == $args['fields'] ) {
+			$hierarchical = false;
+		}
+		if ( $args['hide_empty'] && !$hierarchical ) {
+			$this->sql_clauses['where']['count'] = 'tt.count > 0';
+		}
+
+		$number = $args['number'];
+		$offset = $args['offset'];
+
+		// Don't limit the query results when we have to descend the family tree.
+		if ( $number && ! $hierarchical && ! $child_of && '' === $parent ) {
+			if ( $offset ) {
+				$limits = 'LIMIT ' . $offset . ',' . $number;
+			} else {
+				$limits = 'LIMIT ' . $number;
+			}
+		} else {
+			$limits = '';
+		}
+
+
+		if ( ! empty( $args['search'] ) ) {
+			$this->sql_clauses['where']['search'] = $this->get_search_sql( $args['search'] );
+		}
+
+		// Meta query support.
+		$join = '';
+		$distinct = '';
+
+		// Reparse meta_query query_vars, in case they were modified in a 'pre_get_terms' callback.
+		$this->meta_query->parse_query_vars( $this->query_vars );
+		$mq_sql = $this->meta_query->get_sql( 'term', 't', 'term_id' );
+		$meta_clauses = $this->meta_query->get_clauses();
+
+		if ( ! empty( $meta_clauses ) ) {
+			$join .= $mq_sql['join'];
+			$this->sql_clauses['where']['meta_query'] = preg_replace( '/^\s*AND\s*/', '', $mq_sql['where'] );
+			$distinct .= "DISTINCT";
+
+		}
+
+		$selects = array();
+		switch ( $args['fields'] ) {
+			case 'all':
+			case 'all_with_object_id' :
+			case 'tt_ids' :
+			case 'slugs' :
+				$selects = array( 't.*', 'tt.*' );
+				if ( 'all_with_object_id' === $args['fields'] && ! empty( $args['object_ids'] ) ) {
+					$selects[] = 'tr.object_id';
+				}
+				break;
+			case 'ids':
+			case 'id=>parent':
+				$selects = array( 't.term_id', 'tt.parent', 'tt.count', 'tt.taxonomy' );
+				break;
+			case 'names':
+				$selects = array( 't.term_id', 'tt.parent', 'tt.count', 't.name', 'tt.taxonomy' );
+				break;
+			case 'count':
+				$orderby = '';
+				$order = '';
+				$selects = array( 'COUNT(*)' );
+				break;
+			case 'id=>name':
+				$selects = array( 't.term_id', 't.name', 'tt.count', 'tt.taxonomy' );
+				break;
+			case 'id=>slug':
+				$selects = array( 't.term_id', 't.slug', 'tt.count', 'tt.taxonomy' );
+				break;
+		}
+
+		$_fields = $args['fields'];
+
+		/**
+		 * Filters the fields to select in the terms query.
+		 *
+		 * Field lists modified using this filter will only modify the term fields returned
+		 * by the function when the `$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";
+
+		if ( ! empty( $this->query_vars['object_ids'] ) ) {
+			$join .= " INNER JOIN {$wpdb->term_relationships} AS tr ON tr.term_taxonomy_id = tt.term_taxonomy_id";
+		}
+
+		$where = implode( ' AND ', $this->sql_clauses['where'] );
+
+		/**
+		 * Filters 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( 'fields', 'join', 'where', 'distinct', 'orderby', 'order', 'limits' ), $taxonomies, $args );
+
+		$fields = isset( $clauses[ 'fields' ] ) ? $clauses[ 'fields' ] : '';
+		$join = isset( $clauses[ 'join' ] ) ? $clauses[ 'join' ] : '';
+		$where = isset( $clauses[ 'where' ] ) ? $clauses[ 'where' ] : '';
+		$distinct = isset( $clauses[ 'distinct' ] ) ? $clauses[ 'distinct' ] : '';
+		$orderby = isset( $clauses[ 'orderby' ] ) ? $clauses[ 'orderby' ] : '';
+		$order = isset( $clauses[ 'order' ] ) ? $clauses[ 'order' ] : '';
+		$limits = isset( $clauses[ 'limits' ] ) ? $clauses[ 'limits' ] : '';
+
+		if ( $where ) {
+			$where = "WHERE $where";
+		}
+
+		$this->sql_clauses['select']  = "SELECT $distinct $fields";
+		$this->sql_clauses['from']    = "FROM $wpdb->terms AS t $join";
+		$this->sql_clauses['orderby'] = $orderby ? "$orderby $order" : '';
+		$this->sql_clauses['limits']  = $limits;
+
+		$this->request = "{$this->sql_clauses['select']} {$this->sql_clauses['from']} {$where} {$this->sql_clauses['orderby']} {$this->sql_clauses['limits']}";
+
+		// $args can be anything. Only use the args defined in defaults to compute the key.
+		$key = md5( serialize( wp_array_slice_assoc( $args, array_keys( $this->query_var_defaults ) ) ) . serialize( $taxonomies ) . $this->request );
+		$last_changed = wp_cache_get_last_changed( 'terms' );
+		$cache_key = "get_terms:$key:$last_changed";
+		$cache = wp_cache_get( $cache_key, 'terms' );
+		if ( false !== $cache ) {
+			if ( 'all' === $_fields || 'all_with_object_id' === $_fields ) {
+				$cache = $this->populate_terms( $cache );
+			}
+
+			$this->terms = $cache;
+			return $this->terms;
+		}
+
+		if ( 'count' == $_fields ) {
+			$count = $wpdb->get_var( $this->request );
+			wp_cache_set( $cache_key, $count, 'terms' );
+			return $count;
+		}
+
+		$terms = $wpdb->get_results( $this->request );
+		if ( 'all' == $_fields || 'all_with_object_id' === $_fields ) {
+			update_term_cache( $terms );
+		}
+
+		// Prime termmeta cache.
+		if ( $args['update_term_meta_cache'] ) {
+			$term_ids = wp_list_pluck( $terms, 'term_id' );
+			update_termmeta_cache( $term_ids );
+		}
+
+		if ( empty( $terms ) ) {
+			wp_cache_add( $cache_key, array(), 'terms', DAY_IN_SECONDS );
+			return array();
+		}
+
+		if ( $child_of ) {
+			foreach ( $taxonomies as $_tax ) {
+				$children = _get_term_hierarchy( $_tax );
+				if ( ! empty( $children ) ) {
+					$terms = _get_term_children( $child_of, $terms, $_tax );
+				}
+			}
+		}
+
+		// Update term counts to include children.
+		if ( $args['pad_counts'] && 'all' == $_fields ) {
+			foreach ( $taxonomies as $_tax ) {
+				_pad_term_counts( $terms, $_tax );
+			}
+		}
+
+		// Make sure we show empty categories that have children.
+		if ( $hierarchical && $args['hide_empty'] && is_array( $terms ) ) {
+			foreach ( $terms as $k => $term ) {
+				if ( ! $term->count ) {
+					$children = get_term_children( $term->term_id, $term->taxonomy );
+					if ( is_array( $children ) ) {
+						foreach ( $children as $child_id ) {
+							$child = get_term( $child_id, $term->taxonomy );
+							if ( $child->count ) {
+								continue 2;
+							}
+						}
+					}
+
+					// It really is empty.
+					unset( $terms[ $k ] );
+				}
+			}
+		}
+
+		/*
+		 * When querying for terms connected to objects, we may get
+		 * duplicate results. The duplicates should be preserved if
+		 * `$fields` is 'all_with_object_id', but should otherwise be
+		 * removed.
+		 */
+		if ( ! empty( $args['object_ids'] ) && 'all_with_object_id' != $_fields ) {
+			$_tt_ids = $_terms = array();
+			foreach ( $terms as $term ) {
+				if ( isset( $_tt_ids[ $term->term_id ] ) ) {
+					continue;
+				}
+
+				$_tt_ids[ $term->term_id ] = 1;
+				$_terms[] = $term;
+			}
+
+			$terms = $_terms;
+		}
+
+		$_terms = array();
+		if ( 'id=>parent' == $_fields ) {
+			foreach ( $terms as $term ) {
+				$_terms[ $term->term_id ] = $term->parent;
+			}
+		} elseif ( 'ids' == $_fields ) {
+			foreach ( $terms as $term ) {
+				$_terms[] = (int) $term->term_id;
+			}
+		} elseif ( 'tt_ids' == $_fields ) {
+			foreach ( $terms as $term ) {
+				$_terms[] = (int) $term->term_taxonomy_id;
+			}
+		} elseif ( 'names' == $_fields ) {
+			foreach ( $terms as $term ) {
+				$_terms[] = $term->name;
+			}
+		} elseif ( 'slugs' == $_fields ) {
+			foreach ( $terms as $term ) {
+				$_terms[] = $term->slug;
+			}
+		} elseif ( 'id=>name' == $_fields ) {
+			foreach ( $terms as $term ) {
+				$_terms[ $term->term_id ] = $term->name;
+			}
+		} elseif ( 'id=>slug' == $_fields ) {
+			foreach ( $terms as $term ) {
+				$_terms[ $term->term_id ] = $term->slug;
+			}
+		}
+
+		if ( ! empty( $_terms ) ) {
+			$terms = $_terms;
+		}
+
+		// Hierarchical queries are not limited, so 'offset' and 'number' must be handled now.
+		if ( $hierarchical && $number && is_array( $terms ) ) {
+			if ( $offset >= count( $terms ) ) {
+				$terms = array();
+			} else {
+				$terms = array_slice( $terms, $offset, $number, true );
+			}
+		}
+
+		wp_cache_add( $cache_key, $terms, 'terms', DAY_IN_SECONDS );
+
+		if ( 'all' === $_fields || 'all_with_object_id' === $_fields ) {
+			$terms = $this->populate_terms( $terms );
+		}
+
+		$this->terms = $terms;
+		return $this->terms;
+	}
+
+	/**
+	 * Parse and sanitize 'orderby' keys passed to the term query.
+	 *
+	 * @since 4.6.0
+	 *
+	 * @global wpdb $wpdb WordPress database abstraction object.
+	 *
+	 * @param string $orderby_raw Alias for the field to order by.
+	 * @return string|false Value to used in the ORDER clause. False otherwise.
+	 */
+	protected function parse_orderby( $orderby_raw ) {
+		$_orderby = strtolower( $orderby_raw );
+		$maybe_orderby_meta = false;
+
+		if ( in_array( $_orderby, array( 'term_id', 'name', 'slug', 'term_group' ), true ) ) {
+			$orderby = "t.$_orderby";
+		} elseif ( in_array( $_orderby, array( 'count', 'parent', 'taxonomy', 'term_taxonomy_id', 'description' ), true ) ) {
+			$orderby = "tt.$_orderby";
+		} elseif ( 'term_order' === $_orderby ) {
+			$orderby = 'tr.term_order';
+		} elseif ( 'include' == $_orderby && ! empty( $this->query_vars['include'] ) ) {
+			$include = implode( ',', wp_parse_id_list( $this->query_vars['include'] ) );
+			$orderby = "FIELD( t.term_id, $include )";
+		} elseif ( 'slug__in' == $_orderby && ! empty( $this->query_vars['slug'] ) && is_array( $this->query_vars['slug'] ) ) {
+			$slugs = implode( "', '", array_map( 'sanitize_title_for_query', $this->query_vars['slug'] ) );
+			$orderby = "FIELD( t.slug, '" . $slugs . "')";
+		} elseif ( 'none' == $_orderby ) {
+			$orderby = '';
+		} elseif ( empty( $_orderby ) || 'id' == $_orderby || 'term_id' === $_orderby ) {
+			$orderby = 't.term_id';
+		} else {
+			$orderby = 't.name';
+
+			// This may be a value of orderby related to meta.
+			$maybe_orderby_meta = true;
+		}
+
+		/**
+		 * Filters 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, $this->query_vars, $this->query_vars['taxonomy'] );
+
+		// Run after the 'get_terms_orderby' filter for backward compatibility.
+		if ( $maybe_orderby_meta ) {
+			$maybe_orderby_meta = $this->parse_orderby_meta( $_orderby );
+			if ( $maybe_orderby_meta ) {
+				$orderby = $maybe_orderby_meta;
+			}
+		}
+
+		return $orderby;
+	}
+
+	/**
+	 * Generate the ORDER BY clause for an 'orderby' param that is potentially related to a meta query.
+	 *
+	 * @since 4.6.0
+	 *
+	 * @param string $orderby_raw Raw 'orderby' value passed to WP_Term_Query.
+	 * @return string ORDER BY clause.
+	 */
+	protected function parse_orderby_meta( $orderby_raw ) {
+		$orderby = '';
+
+		// Tell the meta query to generate its SQL, so we have access to table aliases.
+		$this->meta_query->get_sql( 'term', 't', 'term_id' );
+		$meta_clauses = $this->meta_query->get_clauses();
+		if ( ! $meta_clauses || ! $orderby_raw ) {
+			return $orderby;
+		}
+
+		$allowed_keys = array();
+		$primary_meta_key = null;
+		$primary_meta_query = reset( $meta_clauses );
+		if ( ! empty( $primary_meta_query['key'] ) ) {
+			$primary_meta_key = $primary_meta_query['key'];
+			$allowed_keys[] = $primary_meta_key;
+		}
+		$allowed_keys[] = 'meta_value';
+		$allowed_keys[] = 'meta_value_num';
+		$allowed_keys   = array_merge( $allowed_keys, array_keys( $meta_clauses ) );
+
+		if ( ! in_array( $orderby_raw, $allowed_keys, true ) ) {
+			return $orderby;
+		}
+
+		switch( $orderby_raw ) {
+			case $primary_meta_key:
+			case 'meta_value':
+				if ( ! empty( $primary_meta_query['type'] ) ) {
+					$orderby = "CAST({$primary_meta_query['alias']}.meta_value AS {$primary_meta_query['cast']})";
+				} else {
+					$orderby = "{$primary_meta_query['alias']}.meta_value";
+				}
+				break;
+
+			case 'meta_value_num':
+				$orderby = "{$primary_meta_query['alias']}.meta_value+0";
+				break;
+
+			default:
+				if ( array_key_exists( $orderby_raw, $meta_clauses ) ) {
+					// $orderby corresponds to a meta_query clause.
+					$meta_clause = $meta_clauses[ $orderby_raw ];
+					$orderby = "CAST({$meta_clause['alias']}.meta_value AS {$meta_clause['cast']})";
+				}
+				break;
+		}
+
+		return $orderby;
+	}
+
+	/**
+	 * Parse an 'order' query variable and cast it to ASC or DESC as necessary.
+	 *
+	 * @since 4.6.0
+	 *
+	 * @param string $order The 'order' query variable.
+	 * @return string The sanitized 'order' query variable.
+	 */
+	protected function parse_order( $order ) {
+		if ( ! is_string( $order ) || empty( $order ) ) {
+			return 'DESC';
+		}
+
+		if ( 'ASC' === strtoupper( $order ) ) {
+			return 'ASC';
+		} else {
+			return 'DESC';
+		}
+	}
+
+	/**
+	 * Used internally to generate a SQL string related to the 'search' parameter.
+	 *
+	 * @since 4.6.0
+	 *
+	 * @global wpdb $wpdb WordPress database abstraction object.
+	 *
+	 * @param string $string
+	 * @return string
+	 */
+	protected function get_search_sql( $string ) {
+		global $wpdb;
+
+		$like = '%' . $wpdb->esc_like( $string ) . '%';
+
+		return $wpdb->prepare( '((t.name LIKE %s) OR (t.slug LIKE %s))', $like, $like );
+	}
+
+	/**
+	 * Creates an array of term objects from an array of term IDs.
+	 *
+	 * Also discards invalid term objects.
+	 *
+	 * @since 4.9.8
+	 *
+	 * @param array $term_ids Term IDs.
+	 * @return array
+	 */
+	protected function populate_terms( $term_ids ) {
+		$terms = array();
+
+		if ( ! is_array( $term_ids ) ) {
+			return $terms;
+		}
+
+		foreach ( $term_ids as $key => $term_id ) {
+			$term = get_term( $term_id );
+			if ( $term instanceof WP_Term ) {
+				$terms[ $key ] = $term;
+			}
+		}
+
+		return $terms;
+	}
+}