S2member remote api

Hi everybody.

Currently, I’m testing this code, that I modified and copied from here:

  $op['data'] = array(
            'user_id'    => $userid, // A User ID to query the database for.
            'user_login' => $user_login, // OR, a Username to query the database for.
            'user_email' => $email, // OR, an email address to query the database for.
        );
        ini_set('user_agent','Mozilla/4.0 (compatible; MSIE 6.0)');
        $post_data = stream_context_create(array('http' => array('method' => 'POST', 'header' => 'Content-type: application/x-www-form-urlencoded', 'content' => 's2member_pro_remote_op='.urlencode(json_encode($op)))));
        $result    = json_decode(trim(file_get_contents('https://( my domain) .com/?s2member_pro_remote_op=1', false, $post_data)), true);

But, when I run it, I’ve got the error “503 backend fetch failed”
Anyone knows why?
Thanks