Oh this is because you are missing the database class. Copy/paste the class_database.php and functions.php files to your site and it should work. Note you do not have to use select() or other database methods introduced in Mys v1.3.1, the old $adopts->query() and $stmt->fetchObject() still works.
Yeah I did, the config file now uses PHP constants instead of variables. The new database class is being used everywhere. I can help you get rid of the constants though, and then it should be backward-compatible with Mys v1.3.0.
I just need to know what to add to my scripts to make users auto login to the forum when they log in to the site. I fixed whatever error I had and thought I had it working to do this but it doesn't log me in the forum when I log into the main site.
Well the functions_forums.php are what you need of course. You may also look into the new lines I added for register.php and login.php from Mys v1.3.1, since these are what helps new users log into their forum account after registration or logging into the main site.
Oh I am sorry about that, but I really dont understand why you could have messed up your site. The only changes you made to your old scripts were register.php, login.php and functions.php, correct? If so, just post them and I will get them to work for you. Theres no need to start over. Well if you've followed the upgrade procedure and replaced all your old files by the new files, then its indeed over...