8479 PHP authentication

We have a site composed of 2 php/mysql packages. It's similar to scriptlance, but for a different market. Currently, it's got a front end and a back end for the users. Users login to the front end but then have to log in to the back end again which is a project management utility. I need someone to modify the site code so that there is one login, or so that the auth is passed through to each part of the site. I think this is fairly easy, I don't have the time to figure it out. I've already merged the databases so that the whole site is using one database. I think it's a matter of pointing the auth for the one part of the site to the others.