User and group managing

Im trying to build a website in PHP with users in groups.
What is the best way to manage that?
Table with groups, table with users and what group the're in - and the rest in PHP?
Or is there a better way to do this?

Every user is going to be member of a group in the website.

I would do three tables: members, groups, and members_groups cross-reference. This way a member can be in any number of groups, just put the relationship in the cross-reference table.