Hello and welcome fellow programmers.
A WordPress version of PHP-KeyCodes has just been released which has most of the functionality of the standalone PHP/MySQL application PHP-KeyCodes.
The plugin can be viewed and downloaded from the following link:
https://wordpress.org/plugins/withinweb-php-keycodes/
The plugin allows you to sell per-configured license codes, pin numbers, mobile phone numbers or any other similar codes from your WordPress installation using a PayPal account.