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function is not described

update_object_term_cache() WP 2.3.0

Updates the cache for the given term object ID(s).

Note: Due to performance concerns, great care should be taken to only update term caches when necessary. Processing time can increase exponentially depending on both the number of passed term IDs and the number of taxonomies those terms belong to.

Caches will only be updated for terms not already cached.

No Hooks.

Return

null/false. False if all of the terms in $object_ids are already cached.

Usage

update_object_term_cache( $object_ids, $object_type );
$object_ids(string/array) (required)
Comma-separated list or array of term object IDs.
$object_type(array/string) (required)
The taxonomy object type.

Code of update object term cache: wp-includes/taxonomy.php VER 5.1.1

<?php
function update_object_term_cache( $object_ids, $object_type ) {
	if ( empty( $object_ids ) ) {
		return;
	}

	if ( ! is_array( $object_ids ) ) {
		$object_ids = explode( ',', $object_ids );
	}

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

	$taxonomies = get_object_taxonomies( $object_type );

	$ids = array();
	foreach ( (array) $object_ids as $id ) {
		foreach ( $taxonomies as $taxonomy ) {
			if ( false === wp_cache_get( $id, "{$taxonomy}_relationships" ) ) {
				$ids[] = $id;
				break;
			}
		}
	}

	if ( empty( $ids ) ) {
		return false;
	}

	$terms = wp_get_object_terms(
		$ids,
		$taxonomies,
		array(
			'fields'                 => 'all_with_object_id',
			'orderby'                => 'name',
			'update_term_meta_cache' => false,
		)
	);

	$object_terms = array();
	foreach ( (array) $terms as $term ) {
		$object_terms[ $term->object_id ][ $term->taxonomy ][] = $term->term_id;
	}

	foreach ( $ids as $id ) {
		foreach ( $taxonomies as $taxonomy ) {
			if ( ! isset( $object_terms[ $id ][ $taxonomy ] ) ) {
				if ( ! isset( $object_terms[ $id ] ) ) {
					$object_terms[ $id ] = array();
				}
				$object_terms[ $id ][ $taxonomy ] = array();
			}
		}
	}

	foreach ( $object_terms as $id => $value ) {
		foreach ( $value as $taxonomy => $terms ) {
			wp_cache_add( $id, $terms, "{$taxonomy}_relationships" );
		}
	}
}