get_objects_in_term()WP 2.3.0

Retrieve object_ids of valid taxonomy and term.

The strings of $taxonomies must exist before this function will continue. On failure of finding a valid taxonomy, it will return a WP_Error.

The $terms aren't checked the same as $taxonomies, but still need to exist for object IDs to be returned.

It is possible to change the order that object IDs are returned by using $args with either ASC or DESC array. The value should be in the key named 'order'.

1 time — 0.000449 sec (fast) | 50000 times — 13.14 sec (slow) | PHP 7.1.2, WP 4.7.5

No Hooks.

Return

String[]|WP_Error. An array of object IDs as numeric strings on success, WP_Error if the taxonomy does not exist.

Usage

get_objects_in_term( $term_ids, $taxonomies, $args );
$term_ids(int|int[]) (required)
Term ID or array of term IDs of terms that will be used.
$taxonomies(string|string[]) (required)
String of taxonomy name or Array of string values of taxonomy names.
$args(array|string)
Change the order of the object IDs, either ASC or DESC.
Default: array()

Examples

0

#1 Get the ID of all posts from the category

Here we get the IDs of the posts from category 33:

$post_ids = get_objects_in_term( 33, 'category' );

print_r( $post_ids );
/*
Array (
	[0] => 72
	[1] => 372
	[2] => 800
)
*/
0

#2 Get the IDs of all posts from several taxonomies and their elements

Here 33 is the 'category' tax element, and 12 is the 'post_tag' tax element:

$objects = get_objects_in_term( [ 33, 12 ], [ 'category', 'post_tag' ] );

print_r( $objects );
/*
Array (
	[0] => 72
	[1] => 372
	[2] => 800
	[3] => 2818
	[4] => 2971
	[5] => 3755
)
*/
0

#3 Checking the return value

$objects = get_objects_in_term( [ 33, 12 ], [ 'category', 'post_tag' ] );

if( is_wp_error( $objects ) ){
	echo 'The taxonomy is incorrect';
}
elseif( ! $objects ){
	echo 'No objects';
}
else {
	echo 'there are objects!';
	print_r( $objects );
}
0

#4 List of all post tags from the specified category

This example shows how to get a list of all post tags that are in a specified category (in this case, the current category) with the least amount of code.

if( is_category() ){

	$term_id = get_queried_object_id(); // the id of the current category

	// collect the IDs of all nested categories
	$term_ids = get_term_children( $term_id, 'category' );
	array_push( $term_ids, $term_id );

	$post_ids = get_objects_in_term( $term_ids, 'category' );

	if ( $post_ids && ! is_wp_error($post_ids) ) {

		$tags = wp_get_object_terms( $post_ids, 'post_tag' );

		if ( $tags && ! is_wp_error( $tags ) ){ 

			$list = [];
			foreach( $tags as $tag ){
				$list[] = '<a href="'. get_term_link( $tag, 'post_tag') .'">'. esc_html( $tag->name ) .'</a>';
			}

			echo '
			<ul>
				<li>'. implode( "</li>\n<li>", $list ) .'</li>
			</ul>
			';
		}
	}

}

Notes

  • Global. wpdb. $wpdb WordPress database abstraction object.

Changelog

Since 2.3.0 Introduced.

Code of get_objects_in_term() WP 6.0.1

function get_objects_in_term( $term_ids, $taxonomies, $args = array() ) {
	global $wpdb;

	if ( ! is_array( $term_ids ) ) {
		$term_ids = array( $term_ids );
	}
	if ( ! is_array( $taxonomies ) ) {
		$taxonomies = array( $taxonomies );
	}
	foreach ( (array) $taxonomies as $taxonomy ) {
		if ( ! taxonomy_exists( $taxonomy ) ) {
			return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
		}
	}

	$defaults = array( 'order' => 'ASC' );
	$args     = wp_parse_args( $args, $defaults );

	$order = ( 'desc' === strtolower( $args['order'] ) ) ? 'DESC' : 'ASC';

	$term_ids = array_map( 'intval', $term_ids );

	$taxonomies = "'" . implode( "', '", array_map( 'esc_sql', $taxonomies ) ) . "'";
	$term_ids   = "'" . implode( "', '", $term_ids ) . "'";

	$sql = "SELECT tr.object_id FROM $wpdb->term_relationships AS tr INNER JOIN $wpdb->term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy IN ($taxonomies) AND tt.term_id IN ($term_ids) ORDER BY tr.object_id $order";

	$last_changed = wp_cache_get_last_changed( 'terms' );
	$cache_key    = 'get_objects_in_term:' . md5( $sql ) . ":$last_changed";
	$cache        = wp_cache_get( $cache_key, 'terms' );
	if ( false === $cache ) {
		$object_ids = $wpdb->get_col( $sql );
		wp_cache_set( $cache_key, $object_ids, 'terms' );
	} else {
		$object_ids = (array) $cache;
	}

	if ( ! $object_ids ) {
		return array();
	}
	return $object_ids;
}