Piwik\Site::getMainUrl PHP Method

    public function getMainUrl()
    {
        return $this->get('main_url');
    }

 public function render()
 {
     $idSite = Common::getRequestVar('idSite');
     $site = new Site($idSite);
     $url = urldecode(Common::getRequestVar('url', '', 'string'));
     if (!empty($url) && strpos($url, 'http://') !== 0 && strpos($url, 'https://') !== 0) {
         $url = 'http://' . $url;
     }
     if (empty($url) || !UrlHelper::isLookLikeUrl($url)) {
         $url = $site->getMainUrl();
     }
     $dataTable = API::getInstance()->getRank($url);
     /** @var \Piwik\DataTable\Renderer\Php $renderer */
     $renderer = Renderer::factory('php');
     $renderer->setSerialize(false);
     return $this->renderTemplate('getRank', array('urlToRank' => Url::getHostFromUrl($url), 'ranks' => $renderer->render($dataTable)));
 }