gistfile1.php

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

$app->before(function (Request $request) use($app) {
    if (0 === strpos($request->headers->get('Content-Type'), 'application/json')) {
        $data = json_decode($request->getContent(), true);
        if (null === $data) {
            return new Response('{"message":"Problems parsing JSON"}', 400);
        }
        $newRequest = new Request(
            $request->query->all(),
            $request->request->all(),
            $request->attributes->all(),
            $request->cookies->all(),
            $request->files->all(),
            $request->server->all(),
            $content = $data
        );
        $app['request'] = $newRequest;
    }
});