Manual:Hooks/UserGetImplicitGroups

Use cases
This hook may be used as part of an extension that synchronizes the list of available groups with external applications or the host operating system.

Implementation background
MediaWiki supports the assignment of group-based user rights. The list of available groups is defined by three sources: groups hard coded into MediaWiki (*, user, autoconfirmed, emailconfirmed), the keys of the  configuration variable and the groups added or filtered by this hook.

Usage
Implementers return a list of groups that should be added. The source for the list may be a hard coded list, a file, a database table, a third party application, or anything else a programmer's imagination can dream up.