Combine user registration/login sessions and user data between a PHP site and Joomla by jelaniaitch

Background I have a site that is made up of two separate scripts, Joomla and a PHP based freelancer script. I am attempting to make the user data and login credentials common between both sites, so that users do not have to register and login into each script separately… (Budget: $30-$250 USD, Jobs: Joomla, MySQL, PHP)