phpBB3 User Integration with External Script

I have a web site that has phpBB3 installed along with a separate database of users. All of the user functions (login, logout, update password) are working for the main web page, but I need the user functions to also update the phpBB_users table. The web site does have an existing script to add users to the phpbb_users table when a new user joins the site. I need someone to work the following: 1) When the user logs into the site, the user should also be automatically logged in to the phpBB forums, as well. The script will need to set the session and cookies to have the user automatically be logged into the forum. Currently the site allows a user to be logged in for one week before requiring a login. If possible, I would like the new script to allow phpBB to read the cookie info so the user is logged in to the forum for up to one week if the user does not logout. 2) When the user logs out of the site, the user should also get logged out of the phpBB forums. 3) When the user changes the password on the site, the script will need to update the phpbb_users table to update the new password for the user. All of the existing scripts for the web page are written in PHP that connect to mySQL databases.