protected function _getXml()
    {
        if ($this->_xml) {
            return $this->_xml;
        }
        libxml_use_internal_errors();
        $data = simplexml_load_string($this->_getBody());
        if ($data) {
            $this->_xml = $data;

            return $this->_xml;
        }

        return null;
    }