PHP For Beginners router or routes problem

I am watching the series for learning PHP and more. But I am stuck at the "Make a php router" lesson. The problem is "/about" or "/contact" or whatever starts with "/". This problem started when I created controllers folder and router and routes files. When I load the "localhost/" its working perfectly but when I click the other links it says "Not Found. The requested URL was not found on this server.". Can you guys help me for how to figure it? I am using XAMPP for localhost.