get_term_children( int $term_id, string $taxonomy )

Merges all term children into a single array of their IDs.

Description

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.

Parameters

$term_id

(Required) ID of term to get children.

$taxonomy

(Required) Taxonomy name.

Return

(array|WP_Error) List of term IDs. WP_Error returned if $taxonomy does not exist.

Source

File: wp-includes/taxonomy.php 

function get_term_children( $term_id, $taxonomy ) {
	if ( ! taxonomy_exists( $taxonomy ) ) {
		return new WP_Error( 'invalid_taxonomy', __( 'Invalid taxonomy.' ) );
	}

	$term_id = intval( $term_id );

	$terms = _get_term_hierarchy($taxonomy);

	if ( ! isset($terms[$term_id]) )
		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;
}

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Changelog

Changelog
Version Description
2.3.0 Introduced.