public function __construct($feed, $id)
 {
     $cache_f = array('lifetime' => 60 * 60, 'automatic_serialization' => true);
     $cache_b = array('cache_dir' => '/tmp');
     $cache = Zend_Cache::factory('Core', 'File', $cache_f, $cache_b);
     if ($c = $cache->load($id . '_FM')) {
         parent::__construct(null, $c->saveXML());
         $this->_base = $c;
     } else {
         try {
             parent::__construct($feed);
             $this->_base = new Zend_Feed_Rss($feed);
             $cache->save($this->_base, $id . '_FM');
             $this->_base->__wakeup();
         } catch (Zend_Feed_Exception $e) {
         }
     }
 }