Nuevo en Symfony 2.8: usando Symfony como un microframework

// app/MicroKernel.php
use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
use Symfony\Component\Config\Loader\LoaderInterface;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Kernel;
use Symfony\Component\Routing\RouteCollectionBuilder;
 
class MicroKernel extends Kernel
{
    use MicroKernelTrait;
 
    public function registerBundles()
    {
        return array(new Symfony\Bundle\FrameworkBundle\FrameworkBundle());
    }
 
    protected function configureRoutes(RouteCollectionBuilder $routes)
    {
        $routes->add('/', 'kernel:indexAction', 'index');
    }
 
    protected function configureContainer(ContainerBuilder $c, LoaderInterface $loader)
    {
        $c->loadFromExtension('framework', ['secret' => '12345']);
    }
 
    public function indexAction()
    {
        return new Response('Hello World');
    }
}

// app/MicroKernel.php
 
class MicroKernel extends Kernel
{
    use MicroKernelTrait;
 
    public function registerBundles()
    {
        $bundles = array(
            new Symfony\Bundle\FrameworkBundle\FrameworkBundle(),
            new Symfony\Bundle\TwigBundle\TwigBundle(),
        );
 
        if (in_array($this->getEnvironment(), array('dev', 'test'), true)) {
            $bundles[] = new Symfony\Bundle\WebProfilerBundle\WebProfilerBundle();
        }
 
        return $bundles;
    }
 
    protected function configureRoutes(RouteCollectionBuilder $routes)
    {
        $routes->mount('/_wdt', $routes->import('@WebProfilerBundle/Resources/config/routing/wdt.xml'));
        $routes->mount('/_profiler', $routes->import('@WebProfilerBundle/Resources/config/routing/profiler.xml'));
 
        $routes->add('/', 'kernel:indexAction', 'index');
    }
 
    protected function configureContainer(ContainerBuilder $c, LoaderInterface $loader)
    {
        // configurar los bundles
        $c->loadFromExtension('framework', [
            'secret' => '12345',
            'profiler' => null,
            'templating' => ['engines' => ['twig']],
        ]);
 
        $c->loadFromExtension('web_profiler', ['toolbar' => true]);
 
        // añadir parámetros de configuración
        $c->setParameter('mail_sender', '[email protected]');
 
        // registrar servicios
        $c->register('app.markdown', 'AppBundle\\Service\\Parser\\Markdown');
    }
 
    public function indexAction()
    {
        return $this->container->get('templating')->renderResponse('index.html.twig');
    }
}

// app/MicroKernel.php
 
// ...
 
class MicroKernel extends Kernel
{
    use MicroKernelTrait;
 
    public function registerBundles()
    {
        return array(
            new Sensio\Bundle\FrameworkExtraBundle\SensioFrameworkExtraBundle(),
            new Symfony\Bundle\FrameworkBundle\FrameworkBundle(),
            new Symfony\Bundle\TwigBundle\TwigBundle(),
            new AppBundle\AppBundle(),
        );
    }
 
    protected function configureRoutes(RouteCollectionBuilder $routes)
    {
        $routes->mount('/', $routes->import('@AppBundle/Controller', 'annotation'));
    }
 
    protected function configureContainer(ContainerBuilder $c, LoaderInterface $loader)
    {
        $loader->load(__DIR__.'/config/config_'.$this->getEnvironment().'.yml');
        $loader->load(__DIR__.'/config/services.yml');
    }
}

// web/app.php
use Symfony\Component\HttpFoundation\Request;
 
$loader = require __DIR__.'/../app/autoload.php';
require_once __DIR__.'/../app/MicroKernel.php';
 
$app = new MicroKernel('prod', false);
$app->loadClassCache();
 
$app->handle(Request::createFromGlobals())->send();