protected function _ppAddDepthInformation()
    {
        $aTree = [];
        foreach ($this->_aArray as $oCat) {
            $aTree[$oCat->getId()] = $oCat;
            $aSubCats = $oCat->getSubCats();
            if (count($aSubCats) > 0) {
                foreach ($aSubCats as $oSubCat) {
                    $aTree = $this->_addDepthInfo($aTree, $oSubCat);
                }
            }
        }
        $this->assign($aTree);
    }