public function oAuth()
 {
     $weObj = new \Org\Wechat\Wechat(C('WECHAT'));
     $access_token = $weObj->getOauthAccessToken();
     if ($access_token) {
         $this->assign('openId', $access_token['openid']);
         $this->display($_GET['state']);
     } else {
         die('no access!');
     }
 }