public function _mergeVars(Smarty_Internal_Data $data = null)
    {
        if (isset($data)) {
            if (!empty($this->tpl_vars)) {
                $data->tpl_vars = array_merge($this->tpl_vars, $data->tpl_vars);
            }
            if (!empty($this->config_vars)) {
                $data->config_vars = array_merge($this->config_vars, $data->config_vars);
            }
        } else {
            $data = $this;
        }
        if (isset($this->parent)) {
            $this->parent->_mergeVars($data);
        }
    }