/** * Main Off-Canvas Sidebars Menu Meta Box Instance. * * Ensures only one instance of this class is loaded or can be loaded. * * @since 0.3 * @static * @return OCS_Off_Canvas_Sidebars_Menu_Meta_box */ public static function get_instance() { if (is_null(self::$_instance)) { self::$_instance = new self(); } return self::$_instance; }