How to allow some permission and not other using a bitwise system?

I am very interested in writing a class that will help me with different permissions for different users (ie. ACL class.) I have been researching for a great method and bitwise operation stuck out!

I found a good article How to write a permission system using bits and bitwise operations in PHP. The article explains How to handle permissions using bitwise operation.

The only thing that I am not sure on how to do is how to allow a user to write a comment but not post a thread.

so if the permission are set like so:

<?php
 
    $perms = array(
        'can_post' => 1,
        'can_comment' => 2,
        'can_edit' => 4,
        'can_delete' => 8
    );


   $user_perms = 2;    

//CONDITION #1
if ($user_perms & $perms['can_comment']) {
    /* He/She has permission to do this */
} else {
    /* He/She doesn't have permission */
}


//CONDITION #2
if ($user_perms & $perms['can_post']) {
    /* He/She has permission to do this */
} else {
    /* He/She doesn't have permission */
}

?>

so above CONDITION #1 show work fine and the comments should be allowed but //CONDITION #2 should not be allowed because The user does not have a permission to post!

My question, how to allow a user to only comment but not post? to post you will have '001' and to comment you will have '010'.

Once you have your $perms array defined, you can actually create your own maps from it:

// can comment and post but not edit or delete:
$poster = $perms['can_post'] | $perms['can_comment'];

// can edit and delete, but not comment or post:
$janitor = $perms['can_delete'] | $perms['can_edit'];

You can combine any number of permissions with the | operator to build permission values.