OAuth callback with php, what am I doing wrong?

Apparently $_GET[‘code’] is not set when falling to the callback. How can I try to trace the cause of this?
My authorization link:
https://id.twitch.tv/oauth2/authorize?client_id=<myid>&redirect_uri=http://plox.nu/oauth/callback.php&response_type=force_verify&scope=bits:read

The URL it redirects to is clean without any arguments. If I deny access then it will give me an error, but not if I allow it.