/**
  * Determine cache filename
  *
  * @access	private
  */
 private function build_url()
 {
     if (self::ACTIVATED === false) {
         return false;
     }
     if (VSession::renderer() == 'mobile') {
         $this->_url .= 'mobile';
     } elseif (VSession::html5()) {
         $this->_url .= 'html5';
     } else {
         $this->_url .= 'html';
     }
     $this->_url .= '-ctl-' . VGet::ctl();
     if (VGet::ctl() == 'albums' && VGet::album() && !VGet::comments()) {
         $this->_url .= '-album-' . VGet::album();
     } elseif (VGet::ctl() == 'search') {
         foreach (VGet::all() as $key => $value) {
             if ($key != 'ctl') {
                 $this->_url .= '-' . $key . '-' . $value;
             }
         }
     }
 }