Facebook Graph update rsvp status

Question

Hi,

I'm trying to get the update rsvp status working, but nothing happens. The permissions are ok btw

        $access_token = $facebook_session['access_token'];
        $fields_arr = array('access_token' => $access_token);
        $fields = json_encode($fields_arr);             

        $request = "https://graph.facebook.com/[EVENT ID]/attending";
        $c = curl_init();
        curl_setopt($c, CURLOPT_POST, true);
        curl_setopt($c, CURLOPT_POSTFIELDS, $fields);

        $result = curl_exec($c);

The result only returns false .. so no error where I can work with. Anybody a working example?