DOMNode::replaceChild

This function replaces the child oldnode with the passed new node

public function replaceChild<T as DOMNode>(
  DOMNode $newchildobj,
  DOMNode $oldchildobj,
): T;

If the new node is already a child it will not be added a second time. If the replacement succeeds the old node is returned.

Parameters

DOMNode$newchildobj - The new node. It must be a member of the target document, i.e. created by one of the DOMDocument->createXXX() methods or imported in the document by DOMDocument::importNode.
DOMNode$oldchildobj - The old node.