Battle Module
Jamroom Developers
There's probably a lot thats different. The one that jumps to mind is if there are any calls to ????_mysql() then for newer php you need to put an 'i' after it for "improved" _mysqli().
That was one of the broken things.
Jamroom hides a lot of that though if you go through its functions. Jamroom5+ also has 'datastores' which JR4 didn't have. They're really useful. Using them means you don't need to define your SQL so rigidly. Still can if you want, but datastores are a different option. KEY -> VALUE storage structure. Its really neat.