{
   "id": "1423993568",
   "gender": "male",
   ...
}

{
   "error": {
      "message": "Unsupported get request. Please read the Graph API documentation at https://developers.facebook.com/docs/graph-api",
      "type": "GraphMethodException",
      "code": 100
   }
}

http://www.facebook.com/app_scoped_user_id/10152133878666403
  --> https://www.facebook.com/shiffoni
  --> https://graph.facebook.com/shiffoni

{
   "id": "669926402",
   "first_name": "Shiffoni",
   "gender": "female",
   "last_name": "Leonhardt",
   "locale": "de_DE",
   "name": "Shiffoni Leonhardt",
   "username": "shiffoni"
}

$fb = new Facebook(array(
 'appId'  => $app_id,
  'secret' => $app_secret,
  'cookie' => true
));

$fbuser=$fb->api('/me/friends?fields=id,name,gender');