public function referrer($default = null, $attributes = null)
    {
        $referrer = $_SERVER['HTTP_REFERER'] ?? null;

        // Check that referrer came from our site.
        $root = $this->rootUrl(true);
        if ($referrer) {
            // Referrer should always have host set and it should come from the same base address.
            if (stripos($referrer, $root) !== 0) {
                $referrer = null;
            }
        }

        if (!$referrer) {
            $referrer = $default ?: $this->route(true, true);
        }

        if ($attributes) {
            $referrer .= $attributes;
        }

        // Return relative path.
        return substr($referrer, strlen($root));
    }