I have designed a php script an was wondering about a way that I do not allow the customer who buys to install it on more than one domain. I am concerned about the logic of it more than the scripting, but if there is a script available to do such task I would not mind having it :)

Just for anyone who might find this useful, I did not use any software to lock the script to a domain, rather I designed a function which checked the url in the browser against the one I have licensed. and job done!!

This is a little outside the scope of the question, but it follows on,
I think,
from a prior post, about updating installed versions of scripts with the latest versions, you could do something similar to ensure the script running, is licensed & check for updates at the same time.
(PS Obfuscate that part of the script that checks the server_loc)

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