If you want to implement licensing module in downloadable php application that need:
Anti-copy schemes just don't work. See numerous previous posts on this site & elsewhere.
You cannot stop people from copying your code.
You could, I supose obfuscate it, mkaing it very difficult for them to change. And, maybe buried in there (or as a necessary .exe, without whcih your code won't function0, you could 'phone home and gradually build a database of IP addresses that are using your code - although I am not sure what that would get you.
Give up on the idea, plan to erly on lawyers if necessary, and put your efforts into developing your product.