WP_Term_Query::get_terms() WordPress Method

	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 $query Current instance of WP_Term_Query (passed by reference).
		 */
		do_action_ref_array( 'pre_get_terms', array( &$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;
				}
			}
		} else {
			// When no taxonomies are provided, assume we have to descend the tree.
			$has_hierarchical_tax = true;
		}

		if ( ! $has_hierarchical_tax ) {
			$args['hierarchical'] = false;
			$args['pad_counts']   = false;
		}

		// 'parent' overrides 'child_of'.
		if ( 0 < (int) $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 string[] $taxonomies An array of taxonomy names.
		 */
		$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 ) {
				if ( 'count' === $args['fields'] ) {
					return 0;
				} else {
					$this->terms = array();
					return $this->terms;
				}
			}
		}

		// '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 ) ) . "')";
		}

		if ( empty( $args['exclude'] ) ) {
			$args['exclude'] = array();
		}

		if ( empty( $args['include'] ) ) {
			$args['include'] = array();
		}

		$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(
						array(
							'taxonomy'   => reset( $taxonomies ),
							'child_of'   => (int) $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 string[] $taxonomies An array of taxonomy names.
		 */
		$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 ( '' === $args['name'] ) {
			$args['name'] = array();
		} else {
			$args['name'] = (array) $args['name'];
		}

		if ( ! empty( $args['name'] ) ) {
			$names = $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 ( '' === $args['slug'] ) {
			$args['slug'] = array();
		} else {
			$args['slug'] = array_map( 'sanitize_title', (array) $args['slug'] );
		}

		if ( ! empty( $args['slug'] ) ) {
			$slug = implode( "', '", $args['slug'] );

			$this->sql_clauses['where']['slug'] = "t.slug IN ('" . $slug . "')";
		}

		if ( '' === $args['term_taxonomy_id'] ) {
			$args['term_taxonomy_id'] = array();
		} else {
			$args['term_taxonomy_id'] = array_map( 'intval', (array) $args['term_taxonomy_id'] );
		}

		if ( ! empty( $args['term_taxonomy_id'] ) ) {
			$tt_ids = implode( ',', $args['term_taxonomy_id'] );

			$this->sql_clauses['where']['term_taxonomy_id'] = "tt.term_taxonomy_id IN ({$tt_ids})";
		}

		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 ( '' === $args['object_ids'] ) {
			$args['object_ids'] = array();
		} else {
			$args['object_ids'] = array_map( 'intval', (array) $args['object_ids'] );
		}

		if ( ! empty( $args['object_ids'] ) ) {
			$object_ids = implode( ', ', $args['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 'count':
				$orderby = '';
				$order   = '';
				$selects = array( 'COUNT(*)' );
				break;
			default:
				$selects = array( 't.term_id' );
				if ( 'all_with_object_id' === $args['fields'] && ! empty( $args['object_ids'] ) ) {
					$selects[] = 'tr.object_id';
				}
				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 string[] $selects    An array of fields to select for the terms query.
		 * @param array    $args       An array of term query arguments.
		 * @param string[] $taxonomies An array of taxonomy names.
		 */
		$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";
			$distinct = 'DISTINCT';
		}

		$where = implode( ' AND ', $this->sql_clauses['where'] );

		$clauses = array( 'fields', 'join', 'where', 'distinct', 'orderby', 'order', 'limits' );

		/**
		 * Filters the terms query SQL clauses.
		 *
		 * @since 3.1.0
		 *
		 * @param string[] $clauses {
		 *     Associative array of the clauses for the query.
		 *
		 *     @type string $fields   The SELECT clause of the query.
		 *     @type string $join     The JOIN clause of the query.
		 *     @type string $where    The WHERE clause of the query.
		 *     @type string $distinct The DISTINCT clause of the query.
		 *     @type string $orderby  The ORDER BY clause of the query.
		 *     @type string $order    The ORDER clause of the query.
		 *     @type string $limits   The LIMIT clause of the query.
		 * }
		 * @param string[] $taxonomies An array of taxonomy names.
		 * @param array    $args       An array of term query arguments.
		 */
		$clauses = apply_filters( 'terms_clauses', compact( $clauses ), $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']}
		";

		$this->terms = null;

		/**
		 * Filters the terms array before the query takes place.
		 *
		 * Return a non-null value to bypass WordPress' default term queries.
		 *
		 * @since 5.3.0
		 *
		 * @param array|null    $terms Return an array of term data to short-circuit WP's term query,
		 *                             or null to allow WP queries to run normally.
		 * @param WP_Term_Query $query The WP_Term_Query instance, passed by reference.
		 */
		$this->terms = apply_filters_ref_array( 'terms_pre_query', array( $this->terms, &$this ) );

		if ( null !== $this->terms ) {
			return $this->terms;
		}

		// $args can be anything. Only use the args defined in defaults to compute the key.
		$cache_args = wp_array_slice_assoc( $args, array_keys( $this->query_var_defaults ) );

		unset( $cache_args['pad_counts'], $cache_args['update_term_meta_cache'] );

		if ( 'count' !== $_fields && 'all_with_object_id' !== $_fields ) {
			$cache_args['fields'] = 'all';
		}

		$key          = md5( serialize( $cache_args ) . 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 ( 'ids' === $_fields ) {
				$term_ids = wp_list_pluck( $cache, 'term_id' );
				$cache    = array_map( 'intval', $term_ids );
			} elseif ( 'count' !== $_fields ) {
				$term_ids = wp_list_pluck( $cache, 'term_id' );
				_prime_term_caches( $term_ids, $args['update_term_meta_cache'] );
				$term_objects = $this->populate_terms( $cache );
				$cache        = $this->format_terms( $term_objects, $_fields );
			}

			$this->terms = $cache;
			return $this->terms;
		}

		if ( 'count' === $_fields ) {
			$count = $wpdb->get_var( $this->request ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared
			wp_cache_set( $cache_key, $count, 'terms' );
			return $count;
		}

		$terms = $wpdb->get_results( $this->request ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared

		if ( empty( $terms ) ) {
			wp_cache_add( $cache_key, array(), 'terms' );
			return array();
		}

		$term_ids = wp_list_pluck( $terms, 'term_id' );
		_prime_term_caches( $term_ids, false );
		$term_objects = $this->populate_terms( $terms );

		if ( $child_of ) {
			foreach ( $taxonomies as $_tax ) {
				$children = _get_term_hierarchy( $_tax );
				if ( ! empty( $children ) ) {
					$term_objects = _get_term_children( $child_of, $term_objects, $_tax );
				}
			}
		}

		// Update term counts to include children.
		if ( $args['pad_counts'] && 'all' === $_fields ) {
			foreach ( $taxonomies as $_tax ) {
				_pad_term_counts( $term_objects, $_tax );
			}
		}

		// Make sure we show empty categories that have children.
		if ( $hierarchical && $args['hide_empty'] && is_array( $term_objects ) ) {
			foreach ( $term_objects 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( $term_objects[ $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 = array();
			$_terms  = array();
			foreach ( $terms as $term ) {
				if ( isset( $_tt_ids[ $term->term_id ] ) ) {
					continue;
				}

				$_tt_ids[ $term->term_id ] = 1;
				$_terms[]                  = $term;
			}

			$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();
				$term_objects = array();
			} else {
				$terms        = array_slice( $terms, $offset, $number, true );
				$term_objects = array_slice( $term_objects, $offset, $number, true );
			}
		}

		// Prime termmeta cache.
		if ( $args['update_term_meta_cache'] ) {
			$term_ids = wp_list_pluck( $term_objects, 'term_id' );
			update_termmeta_cache( $term_ids );
		}

		wp_cache_add( $cache_key, $terms, 'terms' );
		$terms = $this->format_terms( $term_objects, $_fields );

		$this->terms = $terms;
		return $this->terms;
	}