if ( $u && crypt($pass, $u->password) == $u->password ) {
        $class                  = get_called_class();
        self::$user             = new $class((array)$u, false);
        self::$user->session_id = md5(uniqid(mt_rand(), 1));
        self::$user->expires    = gmdate('Y-m-d H:i:s', time() + 86400); // 1 day
        $try                    = 0;

        while( !self::$user->put() ) {
          self::$user->session_id = md5(uniqid(mt_rand(), 1));
          $try++;
          if ( $try == 5 ) {
            $called[ $user ] = false;

            return false;
          }
        }

        $_SESSION['session_id'] = self::$user->session_id;

        // Save the user agent so we can verify it against future sessions,
        // and remove the login attempts cache item
        $cache->add('_user_session_agent_' . $_SESSION['session_id'], $_SERVER['HTTP_USER_AGENT'], 0, time() + 2592000);
        $cache->delete('_user_login_attempts_' . session_id());

        $called[ $user ] = true;

        return true;
      }