automatically redirect a user when a csrf token is detected

gistfile1.php[345]

    $this->dispatcher->connect('form.validation_error', function(sfEvent $event) {
      $form = $event->getSubject();
      $error = $event['error'];
      
      if(!$form->isCSRFProtected())
      {
        return;
      }
      
      $field_name   = sfForm::getCSRFFieldName();
      
      if(isset($error[$field_name]))
      {
        if(sfContext::hasInstance())
        {
          $context = sfContext::getInstance();
          $context->getController()->redirect('@homepage');
          
          $context->getUser()->setFlash('notice', 'Session réinitialisée : vous êtes redirigé vers la page d\'accueil, car votre session a expiré.');
          
          throw new sfStopException();
        }
      }
    });