buyit.php

<h1>Cart</h1>
<?php
require 'lib/myLibrary.php';
?>
<p>Your cart consists of <?=$_GET['item']. ' for $' . $inventory[$_GET['item']]/100;?></p>

home.php

<h1>My Storefront</h1>
<?php
// Pulling in a library - this would be everywhere
require 'lib/myLibrary.php';
// loop over our inventory for the main page
// @todo: remove comments - this is a legacy app
echo '<ul>';
foreach ($inventory as $item => $price) {
  echo '<li>' . $item . ' sells for ';
  echo '$' . $price/100;
  echo ' <a href="buyit.php?item='  . $item . '">Buy it!</a></li>';
}
echo '</ul>';

index.php

<?php
// A start towards refactoring
require 'classes/router.php';
require 'classes/request.php';
// First step is to configure current routes
$routes = [
  '/' => 'home.php',
  '/index.php' => 'home.php',
  '/buyit.php' => 'buyit.php'
];
$request = new request($_REQUEST,$_SERVER);
$router = new router($routes, $request);
/**
 * If your router does not match the old route - run through your application
 * otherwise load up the requires again ;)
 */
if (!$router->match()) {
  $app = new application();
  $app->run();
}else {
  require $router->getOldRoute();
}