$data2 = array(
        'access_token' => $access_token,
    );
    $h = curl_init($userinfo_endpoint);
    curl_setopt($h, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($h, CURLOPT_TIMEOUT, 10);
    curl_setopt($h, CURLOPT_POST, true);
    curl_setopt($h, CURLOPT_HTTPHEADER, 
                array('Content-Type: application/x-www-form-urlencoded'));     
    curl_setopt($h, CURLOPT_POSTFIELDS, http_build_query($data2));
    $res = curl_exec($h);