sfWebResponse::addStylesheet PHP Method

    public function addStylesheet($file, $position = '', $options = array())
    {
        $this->validatePosition($position);
        $this->stylesheets[$position][$file] = $options;
    }

 public static function addAssets(sfWebResponse $response)
 {
     $response->addStylesheet('yui/treeview/assets/skins/qubit/treeview-skin', 'first');
     $response->addJavaScript('/vendor/yui/treeview/treeview-min', 'last');
     $response->addJavaScript('/vendor/yui/dragdrop/dragdrop-min', 'last');
     $response->addJavaScript('treeView', 'last');
 }