Get user approved permissions in facebook graph API

After I add a permission, the user has开发者_运维技巧 to remove the app and add it again, in order to grant new permission. The weird thing is that when I request a permission that the user hasn't approved, I don't get an error, but rather only an empty result set.

How do I check if the user approved a permission?

It is quite simple as you can just use the openn graph API to get that information

https://graph.facebook.com/me/permissions?access_token=....