public function getHTTPDepth($default = self::DEPTH_INFINITY)
    {
        // If its not set, we'll grab the default
        $depth = $this->httpRequest->getHeader('Depth');

        if (is_null($depth)) {
            return $default;
        }

        if ('infinity' == $depth) {
            return self::DEPTH_INFINITY;
        }

        // If its an unknown value. we'll grab the default
        if (!ctype_digit($depth)) {
            return $default;
        }

        return (int) $depth;
    }