Don't judge the code... it suppose to be crap, this is just a very simple front controller I tend to use for quick mockups or playing with composer packages.

index.php

<?php
define('ROOT_DIR', __DIR__ . '/../');
define('VENDOR_DIR', ROOT_DIR. 'vendor/');
define('PUBLIC_DIR', ROOT_DIR . 'public/');
define('ROUTES_DIR', ROOT_DIR . 'routes/');
define('VIEW_DIR', ROOT_DIR . 'views/');
define('CACHE_DIR', ROOT_DIR . 'cache/');

// Include libs
require( VENDOR_DIR . 'autoloader.php' );

// Now lets sort out twig
$views = new Twig_Loader_Filesystem(VIEW_DIR);

// Add public dir for grabing assets
$views->addPath(PUBLIC_DIR);

$twig = new Twig_Environment($views, array(
  'cache' => CACHE_DIR . 'twig',
  'auto_reload' => true,
  'strict_variables' => false,
  'debug' => true
));

// Add debug functionality
$twig->addExtension(new Twig_Extension_Debug());

// Call any php function from within the templates
$twig->addFunction(
  new Twig_SimpleFunction('php_*', function(){
    $arg_list = func_get_args();
    $function = array_shift($arg_list);

    return call_user_func_array($function, $arg_list);
  })
);

// Setup RedBeanPHP
R::setup('mysql:host=localhost;dbname=db', 'user', 'pass');

// Define data array
$data = array();
// Routes, all the routes!
$route = strtolower($_SERVER['REQUEST_URI']);

switch( $route ){
  case '/who':
  case '/technology':
  case '/platforms':
  case '/development':
  case '/join-us':
  case '/love-to-hear-from-you':
    $data['route'] = substr($route, 1);
    $view = $data['route'] . '.twig';
  break;

  case ( preg_match('/^\/news/', $route) ? true : false ):
    $data['route'] = 'news';
    $view = 'news.twig';
  break;

  case '/':
    $data['route'] = 'index';
    $view = 'index.twig';
  break;

  default:
    header($_SERVER['SERVER_PROTOCOL'] . ' 404 Not Found');
    $data['http_code'] = '404';
    $data['route'] = 'error';
    $view = 'error' . '.twig';
  break;
}

// Do we have any route data to grab?
// These will also handle any POST/GET specific to the route
// Don't see the need of complicating this by making it non-procedural
if( isset($data['route']) ){
  $routeController = ROUTES_DIR . $data['route'] . '.php';

  if( file_exists($routeController) ){
    include $routeController;
  }
}

// POST/REDIRECT/GET
if ( $_SERVER['REQUEST_METHOD'] === 'POST' ) {
  header("Location: " . $_SERVER['REQUEST_URI']);
  exit();
}

if( isset($_SESSION['message']) ){
  $data['message'] = $_SESSION['message'];
  unset($_SESSION['message']);
}

// That's it, now lets output the view
echo $twig->render($view, $data);