WP/phpBB session issue

I’ve had phpBB running for years and now I’m trying to integrate WP and phpBB. Basically the only thing I want to achieve is to keep phpBB session alive during visits to WP, so that the phpBB nick can be used when commenting in WP.

I’ve nailed the problem to this line in phpbb file common.php (included in “global session” snippet):

include($phpbb_root_path . 'includes/functions.'.$phpEx);

Everything is okay before this line, nothing comes out after (nor from the file itself). Are there any known issues in that specific file when fetching it from WordPress application?

I found a couple functions in both phpBB and WP by the same name, but I really don’t know what to do with them.