I going to implement ACL (Access control list) in my php website.

In my system user have sum a of roles and permission.

Main algorithm is as follows:

```
permissions = (permissions_by_role + permission_for_user) - user_banned_permission

```

so I have three arrays and get those values from database.

For the first part I use this 

```
 $permissions = array_unique(array_merge($permission_by_role, $permission_by_user));

```

How can I remove my banned permission from permission array?
Now I have these two arrays:

```
$permissions and $permission_banned_for_user[]

```