public function __construct()
 {
     //解决flash上传的cookie问题
     if (isset($_POST['PHPSESSIONID'])) {
         $session_id = Crypt::decrypt(trim($_POST['PHPSESSIONID']));
         if (!empty($session_id)) {
             session_id($session_id);
             Session::setId($session_id);
         }
     }
     parent::__construct();
     $this->model = new Attachment();
 }