adding payment module to a script

hello i have a payment processor script it's an old one i want to add to it some payment gateway [login to view URL] [login to view URL] [login to view URL] and it seem it's written in 2003 this script if it's possible to enhance his core with advanced php version it's mean a rewrite enhanced security etc.. and adding some extra features of your choice if you can get some imagination but not required . if you can do this & it's a easy job. the script is attached to this description in zip format