Frontend\Core\Engine\RssItem::setGuid PHP Method

    public function setGuid($link, $isPermaLink = true)
    {
        // redefine var
        $link = (string) $link;
        // if link doesn't start with http, we prepend the URL of the site
        if (mb_substr($link, 0, 7) != 'http://') {
            $link = SITE_URL . $link;
        }
        // call parent
        parent::setGuid($link, $isPermaLink);
    }