Symfony\Component\HttpFoundation\Request::getQueryString PHP Method

    public function getQueryString()
    {
        $qs = static::normalizeQueryString($this->server->get('QUERY_STRING'));

        return '' === $qs ? null : $qs;
    }

 /**
  * @param CanonicalUrlEvent $event
  */
 public function generateUrlCanonical(CanonicalUrlEvent $event)
 {
     if ($event->getUrl() !== null) {
         return;
     }
     $parseUrlByCurrentLocale = $this->getParsedUrlByCurrentLocale();
     if (empty($parseUrlByCurrentLocale['host'])) {
         return;
     }
     // Be sure to use the proper domain name
     $canonicalUrl = $parseUrlByCurrentLocale['scheme'] . '://' . $parseUrlByCurrentLocale['host'];
     // preserving a potential subdirectory, e.g. http://somehost.com/mydir/index.php/...
     $canonicalUrl .= $this->request->getBaseUrl();
     // Remove script name from path, e.g. http://somehost.com/index.php/...
     $canonicalUrl = preg_replace("!/index(_dev)?\\.php!", '', $canonicalUrl);
     $path = $this->request->getPathInfo();
     if (!empty($path) && $path != "/") {
         $canonicalUrl .= $path;
         $canonicalUrl = rtrim($canonicalUrl, '/');
     } else {
         $queryString = $this->request->getQueryString();
         if (!empty($queryString)) {
             $canonicalUrl .= '/?' . $queryString;
         }
     }
     $event->setUrl($canonicalUrl);
 }