/**
  * chek if this is an ajax-request
  */
 public function preDispatch()
 {
     if (!isset($_SERVER['HTTP_X_REQUESTED_WITH']) && !($_SERVER['HTTP_X_REQUESTED_WITH'] == 'XMLHttpRequest')) {
         header('Location: http://' . $_SERVER['HTTP_HOST']);
         exit;
     }
     parent::preDispatch();
 }