I've personaly not used phpBB, but it was mentioned to me by a person that uses phpBB that a modification would be good for them to use PHP:IRC with phpBB. Since phpBB is in the same family of coding of sorts I've worked on some small modifications....
I've noticed others are working on modifications to get (fill in favorite IRC applet name here) to work with phpBB, depending on how you have your IRC applet client setup this modification could potentialy work for you aswell. (For example CGI:IRC this works with easily you just need to change the path and stuff.)
The modification is only tested for subSilver but should work easily with others. I'll work on it for other styles as they are asked for. If there are other methods wanted for displaying PHP:IRC within phpBB pop a few suggestions and I'll look into it.
Screen Shot:
http://phpirc.sourceforge.net/phpBB.gif
What does this modification do exactly?
*Uses username of logged in user for nickname.
*If not logged the nickname is PHPIRC-rand(0,1000).
*Auto join a channel, or channels.
Things being thought about:
*Using the ip banning from inside phpBB for PHP:IRC (I've not even looked at the admin tools of phpBB yet though to see if it's possable/to what extent.)
*A option to requiring a valid session from phpBB to use PHP:IRC.