Replace content of node using PHP and XPath - php

Question

I have a string of 'source html' and a string of 'replacement html'. In the 'source html' I want to look for a node with a specific class and replace its content with my 'replacement html'. I have tried using the replaceChild method, but this seems to require that I traverse a level up (parentNode).
This doesn't work
$dom = new DOMDocument;
$dom->loadXml($sourceHTML);
$replacement = $dom->createDocumentFragment();
$replacement->appendXML($replacementHTML);
$xpath = new DOMXPath($dom);
$oldNode = $xpath->query('//div[contains(#class,"arrangement--index__field-dato")]')->item(0);
$oldNode->replaceChild($replacement, $oldNode);
This works, but it's not the content which is being replaced
$dom = new DOMDocument;
$dom->loadXml($sourceHTML);
$replacement = $dom->createDocumentFragment();
$replacement->appendXML($replacementHTML);
$xpath = new DOMXPath($dom);
$oldNode = $xpath->query('//div[contains(#class,"arrangement--index__field-dato")]')->item(0);
$oldNode->parentNode->replaceChild($replacement, $oldNode);
How do I replace the content or the node I have queried for?

Answer 1

Instead of replacing the child node, loop over it's children, drop them and insert the new content as child node. Something like
foreach ($oldNode->childNodes as $child)
$oldNode->removeChild($child);
$oldNode->appendChild($replacement);
This will replace the contents (children) instead of the node itself.

Answer 2

This seems to work!
$dom = new DOMDocument;
$dom->loadXml($sourceHTML);
$replacement = $dom->createDocumentFragment();
$replacement->appendXML($replacementHTML);
$xpath = new DOMXPath($dom);
$oldNode = $xpath->query('//div[contains(#class,"arrangement--index__field-dato")]')->item(0);
$oldNode->removeChild($oldNode->firstChild);
$oldNode->appendChild($replacement);