Hi
I just made a simple forum for a site I'm working on.
You can see it at http://damien.x.i8t.com/begripgaming/index.php - when it's up.
I don't know what kind of info you would like. But my idea was like this.
I have departments wich contain categories wich contain posts. They are represented by forum_departments, forum_categories and forum_posts tables in the db. They are linked together via id's. So that forum_category for example have a field named department wich contains the id of the department the category recides in. categories and departments also have description and name.
forum_posts contain, amongst other things:
id
header
body
category - id of category the post recides in
poster - id of the posting user
is_topic - integer that == 1 if the post is a topic
reply_to - if this is a reply to a topic this hold the id of the topic post
time - timestamp of when the post was done
Using this I can list all categories, click on one and list all the posts that are topics and recide in the category. And once I click a topic list all the posts that are replies to that post. That was how I thought about it. And it all works fine. If there is anything specific you wish to know feel free to ask.
As far as a class goes I didn't use this approach. However, when I was done I felt that a class would have been nice. So next time I will wrap it all up in a class.