use Silex\Application;
use Dafiti\Silex\ContentNegotiationServiceProvider;

$config = [    
    'available_accepts' => [
        'application/json',
        'application/xml'
    ],
    'default_accept'    => 'application/json'
];

$app = new Application();
$app->register(new ContentNegotiationServiceProvider($config));

$app->get("/your-endpoint", function() {
    $data = ["you data to response"];
    
    return new \Dafiti\Silex\Response($data);
});