Make my PHP Scripts secure (may not need any work at all)

Hi, So recently I was hacked by a PHP coder because he couldn't complete a job I had hired him for so I paid him for what he had completed (not what he hadn't completed). I guess he got annoyed and he had placed extract($_REQUEST); in a few of my files. I deleted it from Config, so he shouldn't be able to access my files any more; However, I need all files fully checked and made sure there is no security breach. This may just need looking at, probably no coding needed. But, because of this coder, no one is able to login to the website. I know the file that is the problem, but I can't find the actual issue. extract($_REQUEST); is at the top of the file, but when i delete the line it still doesn't work. So, this file needs slight changes (maybe there is an open tag or syntax issue), it's no big deal.