Check requirements - Tehnari/oidcfed_lib_php_rp GitHub Wiki

PHP v 7.x is recommended (but can work with version 5.6.x).
Install Openssl (should be form the start, but who knows ... :) ).
Start composer to add dependencies.
Was developed in Linux and didn't test with other operating systems.
Read/change variables at parameters.php and classes/configure.php (at this moment is better to check both files).