Example of overriding service, without unnecessary loading

index.php

<?php

require_once __DIR__.'/vendor/.composer/autoload.php';

use Silex\Application;

$app = new Application;
$app['debug'] = true;

$app->register(new Silex\Provider\TwigServiceProvider(), array(
    'twig.path'       => __DIR__.'/views',
    'twig.class_path' => __DIR__.'/vendor/twig/lib',
));

/**
 * Redefine twig service without loading unnecessarily
 */
$app['twig.super'] = $app->raw('twig');
$app['twig'] = $app->share(function($c) {
    $twig = $c['twig.super'];
    // add loaders, extensions etc
    return $twig;
});

$app->get('/', function(Application $app) {
    return $app['twig']->render('index.html.twig', array());
});

$app->get('/notwig', function(Application $app) {
    return 'Hello World';
});

$app->run();