This little script provides you a way to have pretty URLs in your php web site. If you just want to have routes but you do not want to bother with massive php frameworks, you could find this useful
Routing and filtering extension system for yii2 framework that emulates the laravel routing system
This repo is the code used in the DevDojo Creating a PHP Routing System Video Series
Integrates static laravel-like routes and filtering into codeigniter 3.x and 2.x
This project replace the routing system in Drupal 8 to use Redis in storage