Vue CLI 3 prerender-spa-плагин

function toXML($data, $obj = false, $dom) {
    $is_first_level = false;
    if($obj === false) {
        $dom = new DomDocument('1.0');
        $obj = $dom;
        $is_first_level = true;
    }

    if(is_array($data)) {
        foreach($data as $key => $item) {
            $this->toXML($item, $obj->appendChild($dom->createElement($key)), $dom);
        }
    }else {
        $obj->appendChild($dom->createTextNode($data));
    }

    if($is_first_level) {
        $obj->formatOutput = true;
        return $obj->saveXML();
    }
    return $obj;
}