This document provides instructions for creating a simple router in PHP. It begins by explaining the goals of displaying a calendar and handling a birthday form. It then discusses .htaccess files and how they can redirect all requests to an index.php file. The index.php file acts as a router, checking the $_SERVER variable to determine which page has been requested and including the appropriate PHP file. Specific routes are shown for the calendar, birthday, and index pages. Testing the application is recommended to confirm it is routing requests correctly.