wxjs 之 微擎php中獲取openid

//獲取openid

    public function doPageOpenid(){
        global $_W, $_GPC;
        $res=pdo_get('sakura_system',array('uniacid'=>$_W['uniacid']));

        //聲明CODE，獲取小程序傳過來的CODE
        $code = $_GPC['code'];
        //配置appid
        $appid = $res['appid'];
        //配置appscret
        $secret = $secret=$res['appsecret'];
        //api接口
        $api = "https://api.weixin.qq.com/sns/jscode2session?appid=".$appid."&secret=".$secret."&js_code=".$code."&grant_type=authorization_code";
        //獲取GET請求
        function httpGet($url){
            $curl = curl_init();
            curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
            curl_setopt($curl, CURLOPT_TIMEOUT, 500);
            curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, true);
            curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, true);
            curl_setopt($curl, CURLOPT_URL, $url);
            $res = curl_exec($curl);
            curl_close($curl);
            return $res;
        }
        //發送
        $str = httpGet($api);
        print_r($str);
    }

無法獲取openid的原因：

1.函數問題

2.參數問題，如：appsecret is invalid 等。