Easy Way of Checking Forum Permisison with Array of ID's?

[ZomgStuff]

I don't have a great grasp of bitfields and how they work, but here is my dilema.

How can I check to see whether a certain user can view a forum by it's forumid without actually being in that forum, just for referencing like in an array?

Thanks.

[Dismounted]

PHP Code:

$mypermissions = fetch_permissions($forumid); 

[ZomgStuff]

Thanks!