src/ContentNegotiationServiceProvider.php
public function validateRequestContentType(Request $request, Application $app)
    {
        // Define the "form" format so we can use it for validation
        $request->setFormat("form", array("application/x-www-form-urlencoded", "multipart/form-data"));

        $format = $request->getContentType();
        if (strlen($request->getContent()) > 0 && !in_array($format, $app["conneg.requestFormats"])) {
            // The request has a body but it is not a supported media type
            throw new UnsupportedMediaTypeHttpException();
        }
    }
public function validateRequestContentType(Request $request, Application $app)
    {
        // Define the "form" format so we can use it for validation
        $request->setFormat("form", array("application/x-www-form-urlencoded", "multipart/form-data"));

        $format = $request->getContentType();
        if (strlen($request->getContent()) > 0 && !in_array($format, $app["conneg.requestFormats"])) {
            // The request has a body but it is not a supported media type
            throw new UnsupportedMediaTypeHttpException();
        }
    }
This before middleware validates that the request body is in a format
that the application understands.

@param Request $request
@throws UnsupportedMediaTypeHttpException