protected function addItem($loc, $priority = 0.5, $changeFreq = null, $lastmod = null)
 {
     // TODO
     $priority = '0.5';
     fwrite($this->currentSitemap, "   <url>\n");
     fwrite($this->currentSitemap, "      <loc>{$loc}</loc>\n");
     if ($lastmod != null) {
         fwrite($this->currentSitemap, "      <lastmod>{$lastmod}</lastmod>\n");
     }
     if ($changeFreq != null) {
         fwrite($this->currentSitemap, "      <changefreq>{$changeFreq}</changefreq>\n");
     }
     fwrite($this->currentSitemap, "      <priority>{$priority}</priority>\n");
     fwrite($this->currentSitemap, "   </url>\n");
     $this->itemsAdded++;
     $this->itemsAddedCurrent++;
     if ($this->verbose) {
         Logging::debug($this->itemsAddedCurrent . ' - ' . $loc);
     }
     // Laut Protokoll dürfen bis zu 50000 Einträge in eine Sitemap. Damit kommt man
     // aber oft über die erlaubten 10 MB. Daher wird das hier auf 45000 begrenzt
     if ($this->itemsAddedCurrent >= 45000) {
         $this->createSitemap();
     }
 }