What's not mentioned here is that DOMNode::appendChild() can also be used to move an existing node to another part of the DOMDocument, e.g.
<?php
$doc = new DOMDocument();
$doc->loadXML("<foobar><bar/><foo/></foobar>");
$bar = $doc->documentElement->firstChild;
$foo = $doc->documentElement->lastChild;
$foo->appendChild($bar);
print $doc->saveXML();
?>
This produces:
<?xml version="1.0"?>
<foobar><foo><bar/></foo></foobar>
Note that the nodes "<foo/>" and "<bar/>" were siblings, i.e. the first and last child of "<foobar>" but using appendChild() we were able to move "<bar/>" so that it is a child of "<foo/>".
This saves you the trouble of doing a DOMNode::removeChild($bar) to remove "<bar/>" before appending it as a child of "<foo/>".
Kris Dover
