WHMCS - add client automatically into Client Group

Question

Does anybody know of a way to add new WHMCS client, automatically into a client group? Ideally using a Hook, that will allow configuring multiple products into multiple client groups.

For example:

• If client orders product A, they are added to Client Group A.
• If client orders product B, they are added to Client Group B.

I have tried looking for a solution on WHMCS forums and Google - without luck. This is the closest I have come:

https://github.com/Katamaze/WHMCS-Action-Hook-Factory/blob/master/hooks/AssignClientToGroupBasedOnPurchasedProduct_v2.php

But it seems to fail on PHP 8.1.