Peter

Mcrypt is deprecated in PHP 7.2 now, try libsodium plus the built in hashing and password functions like: Mcrypt https://www.php.net/manual/en/intro.mcrypt.php Alternatives: https://www.php.net/manual/en/refs.crypto.php

https://www.zend.com/blog/libsodium-and-php-encrypt

The code is very well written and easy to follow, if you have some experience with PHP it won't be too hard to understand the flow.