src/Request.php
protected function getFormatFromUri($requestedUri)
    {
        $uriParts = explode('?', $requestedUri, 2);
        $uriWithoutGet = reset($uriParts);
        $uriAndFormat = explode('.', $uriWithoutGet);
        if (count($uriAndFormat) >= 2) {
            return end($uriAndFormat);
        }
        return null;
    }
protected function getFormatFromUri($requestedUri)
    {
        $uriParts = explode('?', $requestedUri, 2);
        $uriWithoutGet = reset($uriParts);
        $uriAndFormat = explode('.', $uriWithoutGet);
        if (count($uriAndFormat) >= 2) {
            return end($uriAndFormat);
        }
        return null;
    }
Get the format from the url.

If the request had a suffix in the url, this method will discover it and
return it.

@example /hello-world.json => json
@example /hello-world.xml => xml
@example /hello-world => null

@param $requestedUri
@return string|null