function get_all_category_ids() {
	_deprecated_function( __FUNCTION__, '4.0.0', 'get_terms()' );

	if ( ! $cat_ids = wp_cache_get( 'all_category_ids', 'category' ) ) {
		$cat_ids = get_terms(
			array(
				'taxonomy' => 'category',
				'fields'   => 'ids',
				'get'      => 'all',
			)
		);
		wp_cache_add( 'all_category_ids', $cat_ids, 'category' );
	}

	return $cat_ids;
}