Add credits to account after Paypal(button) purchase - PHP

Hello, We need someone to add(write) a script to our website which will credit one of our member's account after purchasing credits through a Paypal button. This should be simple for a professional. There is a similar script already in our website that you might be able to simply alter a bit and utilize. There is much more work if you prove yourself efficient, skillful and show great communication skills. We are currently looking to add a PHP/MySQL programmer to our team. cURL scripting is a plus! Thank you, jrmhan