PHP License Generator

PHP License Generator / Online Serial Number Generator looking for a script that allows me to generate licenses/serial numbers for PHP based script that i'm making its a social website, I need this script to be 'binded' to domains. This means the specific license serial number will only unlock the script on a specified domain and no where else. That way i can stop cloning of the scripts... I will need the script with number to stay on the site to work with that .com or etc name ONLY If a user removes that part of the code the site should shut down. once they buy a site from my website it must Generate a code to work ONLY with that name, I have a place in the admin on the site to Place Lic. questions please ask Please i see the FREE stuff out there need a decent one not top of the line i can buy one for 500usd and is high tech