code: public function xml2array($xml, array &$arr, $parentKey = '')
      {
          if (!$xml) {
              return;
          }
  
          if (count($xml->children()) == 0) {
              $arr[$parentKey] = (string)$xml;
          } else {
              foreach ($xml->children() as $key => $item) {
                  $key = $parentKey ? $parentKey . DS . $key : $key;
                  $this->xml2array($item, $arr, $key);
              }
          }
  
          return $arr;
      }
docs: Flattens an xml tree into an associate array where key represents path
  
  @param Mage_Core_Model_Config_Element $xml
  @param array                          $arr
  @param string                         $parentKey
  @return array|void