wppaste
WordPress

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

Since
2.3.0
Source
wp-includes/taxonomy.php:1176
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.

Compatibility

WordPress
since 2.3.0
PHP
7.4–8.6-dev
  • 6.7.7
  • 6.8.8
  • 6.9.7
  • 7.0.4
  • 7.1.0

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$term_idint
ID of term to get children.
$taxonomystring
Taxonomy name.

Return value

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

Performance profile

How much work a call to get_term_children() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.

Cost class
Heavy

Reaches the database via get_terms().

Scaling
Scales with input

The body loops, so the work grows with what you pass in.

Instructions
14–21

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 44.

Plugin surface
None

Nothing here hands control to plugin code.

Called by
3

3 places in core call this, so the cost is paid more often than your own code shows.

What it touches

  • optionoption read or writeget_option()one call below get_term_children()
  • querycontent queryget_terms()one call below get_term_children()

Further down the call graph this can also reach hook, cache, serialize and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.

What one call costs · 2 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost get_term_children() can have, taken from its control-flow graph on PHP 8.5.

WhenInstructionsCalls it makes
!taxonomy_exists()14taxonomy_exists(), __()
taxonomy_exists()15–21taxonomy_exists(), _get_term_hierarchy()

Across PHP versions

Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 44 instructions, 14–21 executed per call, 6 branches. The work does not change between versions.

An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.

Uses · 5

Used by · 3

Source code

View on Trac View on GitHub 

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;}

Changelog

Introduced in 2.3.0. Unchanged from 6.7.7 through 7.1.0.

  1. 6.7.7
  2. 6.8.8
  3. 6.9.7
  4. 7.0.4
  5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data
Generated from the wordpress-develop 7.0.4 tag, from src/wp-includes/taxonomy.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.
Corrections
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