get_term_children( int $term_id, string $taxonomy ): array|WP_Error

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

Contents

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.

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Parameters

$term_id int Required
ID of term to get children.
$taxonomy string Required
Taxonomy name.

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Return

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

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Source

File: wp-includes/taxonomy.php. View all references 

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

	$term_id = (int) $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.

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User Contributed Notes

  1. Skip to note 1 content
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    Contributed by Codex —

    A Basic Example
    Used to get an array of children taxonomies and write them out with links in an unordered list.

    <?php
$term_id = 10;
$taxonomy_name = 'products';
$termchildren = get_term_children( $term_id, $taxonomy_name );

echo '<ul>';
foreach ( $termchildren as $child ) {
	$term = get_term_by( 'id', $child, $taxonomy_name );
	echo '<li><a href="' . get_term_link( $child, $taxonomy_name ) . '">' . $term->name . '</a></li>';
}
echo '</ul>';
?>

    This would return something like.

    <ul> 
<li><a href="link_to_term_page">Term 1</a></li>
<li><a href="link_to_term_page">Term 2</a></li>
</ul>
  2. Skip to note 2 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 2You must log in to vote on the helpfulness of this note
    Contributed by adiant —

    Categories and Tags are the two pre-defined Taxonomies. The Taxonomy Name, the second required parameter $taxonomy, is ‘category’ for Categories and ‘post_tag’ for Tags.

    If replacing the deprecated function get_category_children(), which returns a String, note that get_term_children() returns an array of Category IDs if the second parameter $taxonomy is ‘category’.

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