RESTful Versioned API with Silex using Accept header

AcceptHeaderKernelListener.php

<?php

use Symfony\Component\HttpKernel\Event\FilterControllerEvent;
use Symfony\Component\HttpKernel\HttpKernelInterface;
use Symfony\Component\HttpKernel\Event\GetResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

class AcceptHeaderKernelListener implements EventSubscriberInterface
{
    public static function onKernelRequest(GetResponseEvent $event)
    {
        if ($event->getRequest()->headers->get('Accept') != '')
        {
            $raw_accepts = explode(',', $event->getRequest()->headers->get('Accept'));

            $accepts = array_map('trim', $raw_accepts);

            $event->getRequest()->request->set('_accept', $accepts);

            $event->getDispatcher()->addSubscriber(new \AcceptHeaderMatchEventListener($event->getRequest()));
        }
    }

    public static function getSubscribedEvents()
    {
        return array(KernelEvents::REQUEST => array('onKernelRequest', 100));
    }

}

AcceptHeaderMatchEventListener.php

<?php

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\Routing\Matcher\UrlMatcher;
use Symfony\Component\Routing\Matcher\UrlMatcherEvent;
use Symfony\Component\HttpFoundation\Request;

class AcceptHeaderMatchEventListener implements EventSubscriberInterface
{
    private $request;

    public function __construct(Request $request)
    {
        $this->request = $request;
    }

    public function onMatch(UrlMatcherEvent $event)
    {
        foreach($this->request->request->get('_accept') as $accept)
        {
            if (preg_match('/^('.$event->getRoute()->getRequirement('_accept').')$/', $accept))
            {
                $event->getRoute()->setDefault('accept_header', $accept);
                $event->setStatus(UrlMatcherEvent::REQUIREMENT_MATCH);

                return;
            }
        }

        $event->setStatus(UrlMatcherEvent::REQUIREMENT_MISMATCH);
    }

    public static function getSubscribedEvents()
    {
        return array(UrlMatcher::EVENT_HANDLE_REQUIREMENTS => array('onMatch', 100));
    }
}

AcceptHeaderRoute.php

<?php

use Silex\Route;

class AcceptHeaderRoute extends Route
{
    public function accept($content_types)
    {
        $content_regexps = array_map(function($item) { return preg_quote($item, '/'); }, $content_types);

        $this->setRequirement('_accept', implode('|', $content_regexps));

        return $this;
    }
}

AcceptHeaderRoutingTest.php

<?php

use Silex\WebTestCase;
use Symfony\Component\HttpKernel\HttpKernel;
use Silex\Controller;
use Silex\ControllerCollection;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpKernel\KernelEvents;
use Silex\RedirectableUrlMatcher;

class AcceptHeaderRoutingTest extends WebTestCase
{
    /**
     * Creates the application.
     *
     * @return HttpKernel
     */
    public function createApplication()
    {
        $app = new \Silex\Application();

        $app['route_class'] = '\\AcceptHeaderRoute';

        $app['dispatcher']->addSubscriber(new \AcceptHeaderKernelListener());

        $app['url_matcher'] = $app->share(function () use ($app) {
            $matcher = new RedirectableUrlMatcher($app['routes'], $app['request_context']);
            $matcher->setEventDispatcher($app['dispatcher']);
            return $matcher;
        });


        /** @var $controllers1 VersionedRestControllerCollection */
        $controllers1 = $app['controllers_factory'];

        $controllers1->get('/test', function($accept_header) use ($app) {
            if ($accept_header == 'application/ven.test.v1+json')
                $cont = json_encode(array('content' => 'hello'));
            else
                $cont = '<content>hello</content>';

            return new Response($cont, 200, array('Content-Type' => $accept_header));
        })->accept(array('application/ven.test.v1+json', 'application/ven.test.v1+xml'));


        /** @var $controllers1 VersionedRestControllerCollection */
        $controllers2 = $app['controllers_factory'];

        $controllers1->get('/test', function($accept_header) use ($app) {
            if ($accept_header == 'application/ven.test.v2+json')
                $cont = json_encode(array('content' => 'hiya'));
            else
                $cont = '<content>hiya</content>';

            return new Response($cont, 200, array('Content-Type' => $accept_header));
        })->accept(array('application/ven.test.v2+json', 'application/ven.test.v2+xml'));


        $app->mount('/', $controllers1);
        $app->mount('/', $controllers2);


        $app['debug'] = true;
        unset($app['exception_handler']);

        return $app;
    }

    public function testValidV1Call()
    {
        $client = $this->createClient();

        $crawler = $client->request('GET', '/test', array(), array(), array('HTTP_ACCEPT' => 'application/ven.test.v1+xml'));

        $this->assertEquals(200, $client->getResponse()->getStatusCode());

        $result = $client->getResponse()->getContent();

        $this->assertEquals('<content>hello</content>', $result, 'response is correct');
    }

    public function testValidV2Call()
    {
        $client = $this->createClient();

        $crawler = $client->request('GET', '/test', array(), array(), array('HTTP_ACCEPT' => 'application/ven.test.v2+xml'));

        $this->assertEquals(200, $client->getResponse()->getStatusCode());

        $result = $client->getResponse()->getContent();

        $this->assertEquals('<content>hiya</content>', $result, 'response is correct');
    }

    /**
     * @expectedException Symfony\Component\HttpKernel\Exception\NotFoundHttpException
     */
    public function testInvalidV3Call()
    {
        $client = $this->createClient();

        $crawler = $client->request('GET', '/test', array(), array(), array('HTTP_ACCEPT' => 'application/ven.test.v3+xml'));

        $this->assertEquals(404, $client->getResponse()->getStatusCode());
    }
}

You can replace:

$accepts = array_map(function($line) { return trim($line); }, $raw_accepts);

With:

$accepts = array_map('trim', $raw_accepts);

Hah! Thanks. So caught up in the process, I missed something silly-simple.

you should also return something always

                return;