<?php
$dom = new DOMDocument();
$element = $dom->createElement("div");
$element->setAttribute("id", "id1");
$dom->appendChild($element);
$tmp = $dom->createDocumentFragment();
$tmp->appendXML('<h1>Hello <b>World!</b></h1>');
$xpath = new DOMXPath($dom);
$xpath->query("//*[@id='id1']")->item(0)->appendChild($tmp);
echo $dom->saveHTML();
PD9waHAKCiRkb20gPSBuZXcgRE9NRG9jdW1lbnQoKTsKJGVsZW1lbnQgPSAkZG9tLT5jcmVhdGVFbGVtZW50KCJkaXYiKTsKJGVsZW1lbnQtPnNldEF0dHJpYnV0ZSgiaWQiLCAiaWQxIik7CiRkb20tPmFwcGVuZENoaWxkKCRlbGVtZW50KTsKCiR0bXAgPSAkZG9tLT5jcmVhdGVEb2N1bWVudEZyYWdtZW50KCk7CiR0bXAtPmFwcGVuZFhNTCgnPGgxPkhlbGxvIDxiPldvcmxkITwvYj48L2gxPicpOwokeHBhdGggPSBuZXcgRE9NWFBhdGgoJGRvbSk7CiR4cGF0aC0+cXVlcnkoIi8vKltAaWQ9J2lkMSddIiktPml0ZW0oMCktPmFwcGVuZENoaWxkKCR0bXApOwoKZWNobyAkZG9tLT5zYXZlSFRNTCgpOw==