获取朋友的数量使用我的Facebook应用程序

How to get number of friends who are already using my facebook app.

I can get the all the friends who are using the app by using me/friends and i can get the total friends count as total_count,

now can i get the total number of friends who already using the app. i can count the result from me/friends and get the total, but is there anything nicer?

$request = new FacebookRequest(
        $session,
        'GET',
        '/me/friends'
);
$response = $request->execute();
$g_object = $response->getGraphObject();

$g_object => contains the all the friends who are already using the app and users friend count