Hi BuzzLY,
Yes it can be done, but it depends on the application how easy it is. A well written application use a generic class for authentication, and it can be very easy to integrate into a site.
A minimum would be to include the class and some configuration, create a new instance of that class, and use the object methods to authenticate the user.
Unfortunately, phpBB is not so easy :-)
A quick look into the code reveals that it can be possible to use it. common.php load many of the needed files. It looks like this code sets up the environment:
define('IN_PHPBB', true);
$phpbb_root_path = './';
include($phpbb_root_path . 'extension.inc');
include($phpbb_root_path . 'common.'.$phpEx);
$userdata = session_pagestart($user_ip, $forum_id);
init_userprefs($userdata);
It's worth trying.
Roy
