private function buildHiddenFields()
    {
        $this->debug->groupCollapsed(__METHOD__);
        $cfg = $this->form->cfg;
        $printOpts = &$cfg['output'];
        $hiddenFields = '';
        if ($printOpts['inputKey']) {   //  && $cfg['persist_method'] != 'none'
            $hiddenFields .= '<input type="hidden" name="_key_" value="'.\htmlspecialchars($this->keyValue).'" />';
        }
        if (\strtolower($cfg['attribs']['method']) == 'get') {
            $this->debug->warn('get method');
            $urlParts = \parse_url(\html_entity_decode($cfg['attribs']['action']));
            // $attribs['action'] = $urlParts['path'];
            if (!empty($urlParts['query'])) {
                \parse_str($urlParts['query'], $params);
                $fieldNames = array();
                foreach ($this->form->currentFields as $field) {
                    $fieldNames[] = $field->attribs['name'];
                }
                foreach ($params as $k => $v) {
                    if (\in_array($k, $fieldNames)) {
                        continue;
                    }
                    $hiddenFields .= '<input type="hidden" name="'.\htmlspecialchars($k).'" value="'.\htmlspecialchars($v).'" />'."\n";
                }
            }
        }
        $this->debug->log('hiddenFields', $hiddenFields);
        $this->debug->groupEnd();
        return $hiddenFields;
    }