Customize of Distribution PHP/SQL Script

I am looking for someone knowledgeable with PHP , XML and SQL to customize our existing PHP-Script for our website that is capable of automatically deliver pre-created serial keys / Voucher-Codes to our customers via e-mail. The script just needs some adjustments to work with our new payment gateway "Sofortüberweisung". Unfortunately the coder and developer of the script doesnt do any customization, so we try to find a PHP-coder here. The source-code and documentation of the script we bought and actually use will be provided by us. So the freelancer can look into it to adjust the code. The source-code also is very good commented. It should help the coder to understand all functions. Summery: - Adjusting / customizing existing PHP-Script to work with (new) payment gateway "Sofortüberweisung" - Commented source-code of exiting script will be provided - API manual and PHP examples of new payment processor (Sofortüberweisung) will be provided We are looking for a PHP-Coder who supports us in future. Maybe more projects and payment gateways (like Webmoney) are planed soon. I have a budget of $30-$150 in mind for it. The project should be finished as soon as possible. Please feel free to message me with any questions. IMPORTANT!!! PLEASE DO NOT BID BEFORE YOU READ THE (API) MANUAL AND UNDERSTAND ALL FUNCTIONS. Thank you!