Responseオブジェクトを更新してビューを変える

 class fooActions extends sfActions
 {
     public function executeIndex()
         $response   = $this->getContext()->getResponse();
         $html = $response->getContent();
         $html = str_replce('</body>', 'TEST</body>', $html);
         $response->setContent($html);
         return sfView::NONE;
     }
 }