HttpKernel Component
====================

HttpKernel provides the building blocks to create flexible and fast HTTP-based
frameworks.

``HttpKernelInterface`` is the core interface of the Symfony full-stack
framework:

```php
interface HttpKernelInterface
{
    /**
     * Handles a Request to convert it to a Response.
     *
     * @param Request $request A Request instance
     *
     * @return Response A Response instance
     */
    function handle(Request $request, $type = self::MASTER_REQUEST, $catch = true);
}
```

It takes a ``Request`` as an input and should return a ``Response`` as an
output. Using this interface makes your code compatible with all frameworks
using the Symfony components. And this will give you many cool features for
free.

Creating a framework based on the Symfony components is really easy. Here is
a very simple, but fully-featured framework based on the Symfony components:

```php
$routes = new RouteCollection();
$routes->add('hello', new Route('/hello', array('_controller' =>
    function (Request $request) {
        return new Response(sprintf("Hello %s", $request->get('name')));
    }
)));

$request = Request::createFromGlobals();

$context = new RequestContext();
$context->fromRequest($request);

$matcher = new UrlMatcher($routes, $context);

$dispatcher = new EventDispatcher();
$dispatcher->addSubscriber(new RouterListener($matcher));

$resolver = new ControllerResolver();

$kernel = new HttpKernel($dispatcher, $resolver);

$kernel->handle($request)->send();
```

This is all you need to create a flexible framework with the Symfony
components.

Want to add an HTTP reverse proxy and benefit from HTTP caching and Edge Side
Includes?

```php
$kernel = new HttpKernel($dispatcher, $resolver);

$kernel = new HttpCache($kernel, new Store(__DIR__.'/cache'));
```

Want to functional test this small framework?

```php
$client = new Client($kernel);
$crawler = $client->request('GET', '/hello/Fabien');

$this->assertEquals('Fabien', $crawler->filter('p > span')->text());
```

Want nice error pages instead of ugly PHP exceptions?

```php
$dispatcher->addSubscriber(new ExceptionListener(function (Request $request) {
    $msg = 'Something went wrong! ('.$request->get('exception')->getMessage().')';

    return new Response($msg, 500);
}));
```

And that's why the simple looking ``HttpKernelInterface`` is so powerful. It
gives you access to a lot of cool features, ready to be used out of the box,
with no efforts.
