/** * Return an instance of this class. * * @since 1.0.0 * @return object A single instance of this class. */ public static function get_instance($parent = null) { // If the single instance hasn't been set, set it now. if (null == self::$instance) { self::$instance = new self(); } if ($parent !== null) { self::$instance->parent = $parent; } return self::$instance; }