wp_cache_get_last_changed()

wp_cache_get_last_changed( string $group ): string

function wp_cache_get_last_changed( $group ) {
	$last_changed = wp_cache_get( 'last_changed', $group );

	if ( $last_changed ) {
		return $last_changed;
	}

	return wp_cache_set_last_changed( $group );
}