protected function _addDepthInfo($aTree, $oCat, $sDepth = "")
    {
        $sDepth .= "-";
        $oCat->oxcategories__oxtitle->setValue($sDepth . ' ' . $oCat->oxcategories__oxtitle->value);
        $aTree[$oCat->getId()] = $oCat;
        $aSubCats = $oCat->getSubCats();
        if (count($aSubCats) > 0) {
            foreach ($aSubCats as $oSubCat) {
                $aTree = $this->_addDepthInfo($aTree, $oSubCat, $sDepth);
            }
        }

        return $aTree;
    }