I can certainly attest to php being suited to writing forums.

I wrote some (http://900ne.tiraen.com/forums.php) in PHP and MySQL in a few days.

Basically if you want any kind of performance or real customisation (i.e. not just changing the theme), don''t use phpbb - it seriously is bloatware. If you want to fully integrate your forums into your own website, again, phpbb is a bit of a large beast to tame.

So yeah, PHP with any backend database should work fine, it''s very well-suited to the task.