Facebook App. How I can know - friend of user has 0 likes or I haven't permission to see it

For user, that has installed my application I can see permissions $facebook->api("/me/permissions");

But if I asked from user when he installed 开发者_运维问答my app permission to get likes of his friends, when I have array of likes:

array(1) { ["data"]=> array(0) { } }

I don't know if he really has 0 likes, or I haven't permission to see it

$facebook->api("/FRIEND_ID/permissions") also returns array(1) { ["data"]=> array(0) { } }

How I can know it?

You cannot query for a user's friends permissions they've granted unless they've explicitly authed your application. Regarding the 'likes', what exactly are you trying to pull? You can only query for the number of likes a page has, which is not a real user.