Facebook PHP SDK

I'm currently developing a facebook application using a Facebook PHP SDK I could access my profile

$request = new   FacebookRequest($session,'GET','/me');
        $profile = $request->execute()->getGraphObject('Facebook\GraphUser');
        echo $profile->getId();

and now I'm trying to get Id of all my friends my code is

permission

echo ' <a href="'. $helper->getReRequestUrl(['user_friends']).'">Se connecter avec facebook</a>';

my code to get friends id list

$request = new   FacebookRequest($session,'GET','/'.$id.'/friends');

but the result give me juste number of friends

thank you in advance.