How to serve PHP files with .html file extensions using the built-in PHP server

router.php

<?php
  $requestedAbsoluteFile = dirname(__FILE__) . $_SERVER['REQUEST_URI'];

  if (!preg_match('/\.html|\.php$/', $requestedAbsoluteFile)) {
    header('Content-Type: '.mime_content_type($requestedAbsoluteFile));
    return false;
  }
  include_once $requestedAbsoluteFile;


  # Usage: The built-in server included in PHP 5.4.0 doesn’t parse files with 
  # extension .html as PHP, so PHP features like includes or headers etc. don’t work.

  # To overcome this, copy `router.php` into the root of your project directory,
  # open a terminal in this directory and start the server while pointing to 
  # this router file:
  #  $ php -S localhost:8000 router.php
  # Accessing localhost:8000 in your browser now should give you a fully-functioning
  # server with PHP supported on these files. Files not ending in .html or .php
  # are ignored by the router code.
?>