I recently found out that phorum_api_user_check_access calls with 3 parameters don't give the correct results as expected from let's say
phorum_db_user_get($user_id, true)
in 'forum_permissions' and 'group_permissions'.
I tested with these calls:
phorum_api_user_check_access(PHORUM_USER_ALLOW_READ, $forum_id, $user_id)
and
phorum_api_user_check_access(PHORUM_USER_ALLOW_READ, PHORUM_ACCESS_LIST, $user_id).
Would you please test this issue and report?