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get_terms() WP 1.0

Retrieve the terms in a given taxonomy or list of taxonomies.

You can fully inject any customizations to the query before it is sent, as well as control the output with a filter.

The 'get_terms' filter will be called when the cache has the term and will pass the found term along with the array of $taxonomies and array of $args. This filter is also called before the array of terms is passed and will pass the array of terms, along with the $taxonomies and $args.

The 'list_terms_exclusions' filter passes the compiled exclusions along with the $args.

The 'get_terms_orderby' filter passes the ORDER BY clause for the query along with the $args array.

Prior to 4.5.0, the first parameter of get_terms() was a taxonomy or list of taxonomies:

$terms = get_terms( 'post_tag', array(
'hide_empty' => false,
) );

Since 4.5.0, taxonomies should be passed via the 'taxonomy' argument in the $args array:

$terms = get_terms( array(
'taxonomy' => 'post_tag',
'hide_empty' => false,
) );

Notes:

  • Since 4.2.0 Introduced 'name' and 'childless' parameters.
  • Since 4.4.0 Introduced the ability to pass 'term_id' as an alias of 'id' for the orderby parameter. Introduced the 'meta_query' and 'update_term_meta_cache' parameters. Converted to return a list of WP_Term objects.
  • Since 4.5.0 Changed the function signature so that the $args array can be provided as the first parameter. Introduced 'meta_key' and 'meta_value' parameters. Introduced the ability to order results by metadata.
  • Since 4.8.0 Introduced 'suppress_filter' parameter.
Works based on: WP_Term_Query()
✈ 1 time = 0.015166s = extreme slow | 50000 times = 33.29s = very slow PHP 7.1.11, WP 4.9.5
Hooks from function:
Return

Array/Int/WP_Error. List of WP_Term instances and their children. Will return WP_Error, if any of $taxonomies do not exist.

Usage

get_terms( $args, $deprecated );
$args(string/array)
Array or string of arguments. See WP_Term_Query::__construct() for information on accepted arguments.
Default: ''
$deprecated(array)
Argument array, when using the legacy function parameter format. If present, this parameter will be interpreted as $args, and the first function parameter will be parsed as a taxonomy or array of taxonomies.
Default: ''

Code of get_terms: wp-includes/taxonomy.php VER 4.9.8

<?php
function get_terms( $args = array(), $deprecated = '' ) {
	$term_query = new WP_Term_Query();

	$defaults = array(
		'suppress_filter' => false,
	);

	/*
	 * Legacy argument format ($taxonomy, $args) takes precedence.
	 *
	 * We detect legacy argument format by checking if
	 * (a) a second non-empty parameter is passed, or
	 * (b) the first parameter shares no keys with the default array (ie, it's a list of taxonomies)
	 */
	$_args = wp_parse_args( $args );
	$key_intersect  = array_intersect_key( $term_query->query_var_defaults, (array) $_args );
	$do_legacy_args = $deprecated || empty( $key_intersect );

	if ( $do_legacy_args ) {
		$taxonomies = (array) $args;
		$args = wp_parse_args( $deprecated, $defaults );
		$args['taxonomy'] = $taxonomies;
	} else {
		$args = wp_parse_args( $args, $defaults );
		if ( isset( $args['taxonomy'] ) && null !== $args['taxonomy'] ) {
			$args['taxonomy'] = (array) $args['taxonomy'];
		}
	}

	if ( ! empty( $args['taxonomy'] ) ) {
		foreach ( $args['taxonomy'] as $taxonomy ) {
			if ( ! taxonomy_exists( $taxonomy ) ) {
				return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
			}
		}
	}

	// Don't pass suppress_filter to WP_Term_Query.
	$suppress_filter = $args['suppress_filter'];
	unset( $args['suppress_filter'] );

	$terms = $term_query->query( $args );

	// Count queries are not filtered, for legacy reasons.
	if ( ! is_array( $terms ) ) {
		return $terms;
	}

	if ( $suppress_filter ) {
		return $terms;
	}

	/**
	 * Filters the found terms.
	 *
	 * @since 2.3.0
	 * @since 4.6.0 Added the `$term_query` parameter.
	 *
	 * @param array         $terms      Array of found terms.
	 * @param array         $taxonomies An array of taxonomies.
	 * @param array         $args       An array of get_terms() arguments.
	 * @param WP_Term_Query $term_query The WP_Term_Query object.
	 */
	return apply_filters( 'get_terms', $terms, $term_query->query_vars['taxonomy'], $term_query->query_vars, $term_query );
}

Related Functions

From tag: Term (taxonomies terms)

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