It would be nice to have a function which converts a document/node/element into a string.
Anyways, I use the following code snippet to get the innerHTML value of a DOMNode:
<?php
function getInnerHTML($Node)
{
$Body = $Node->ownerDocument->documentElement->firstChild->firstChild;
$Document = new DOMDocument();
$Document->appendChild($Document->importNode($Body,true));
return $Document->saveHTML();
}
?>