code: public function onBeforeControllerAction($controller, $action)
      {
          if (!isset($_SERVER['PASS_THRU']) or $_SERVER['PASS_THRU'] != md5(Yii::$app->params['salt'] . 'PASS')) {
              throw new HttpException(400, 'Invalid request!');
          }
  
          return parent::onBeforeControllerAction($event);
      }
docs: [[@doctodo method_description:onBeforeControllerAction]].
  
  @param unknown $controller
  @param unknown $action
  
  @throws HttpException [[@doctodo exception_description:HttpException]]
  @return unknown