SimpleXML has its own SPL iterator. See http://www.php.net/~helly/php/ext/spl/classSimpleXMLIterator.html . But I guess that there are none for DOM nodes. By the way, two out of three implementations I found over the Net were not recursive, so I wrote my own. Here is the snippet:

<?php

class DOMNodeListIterator implements RecursiveIterator
{
    private
        $nodes,
        $offset;

    function __construct(DOMNodeList $nodes)
    {
        return $this -> nodes = $nodes;
    }
    
    function rewind()
    {
        return $this -> offset = 0;
    }
    
    function current()
    {
        return $this -> nodes -> item($this -> offset);
    }

    function key()
    {
        return $this -> current() -> nodeName;
    }
    
    function next()
    {
        return $this -> offset++;
    }
    
    function valid()
    {
        return $this -> offset < $this -> nodes -> length;
    }
    
    function hasChildren()
    {
        return isset($this -> current() -> childNodes -> length) && $this -> current() -> childNodes -> length > 0;
    }
    
    function getChildren()
    {
        return new self($this -> current() -> childNodes);
    }
}

?>

Remember to use RecursiveIteratorIterator::SELF_FIRST flag when you create your iterator iterator.

<?php

$iterator = new DOMNodeListIterator($document -> childNodes);
$iterator = new RecursiveIteratorIterator($iterator, RecursiveIteratorIterator::SELF_FIRST);

?>

Should work, has just few minutes though. :)

@ tfg_allardyce at gmail dot com

You could loop through the list backwards, that way, you are only ever taking off the last item from the list, and hence wont have disrupted the order.

DOMNodeList::item does not return in constant time!

If you need to iterate over large nodelist then you'd better use standard navigation.

Instead of:

<?php
foreach ($nodelist as $node) {
    // do something
}
?>

you could do:

<?php
$node = $parentnode->firstChild;

do {
    // do something
} while ($node = $node->nextSibling);
?>

calling domnodelist->item($i) with an index $i greater than domnodelist->length - 1 , will return the entire document, will not produce an error, and will not circle back to the start of the list.

DOMNodelist::item can return a DOMElement object, which extends DOMNode class. But it can also return a DOMText object.

<?php
$xml = '
<root>
  <node/>
  <node>
    <sub>more</sub>
  </node>
  <node>
    <sub>another</sub>
  </node>
  <node>value</node>
</root>
';

$doc = new DOMDocument();
$doc->loadXML($xml);

$items = $doc->documentElement->childNodes;
for ($i = 0; $i < $items->length; $i++)
  echo get_class($items->item($i)).PHP_EOL;
?>

Results in this output:

DOMText
DOMElement
DOMText
DOMElement
DOMText
DOMElement
DOMText
DOMElement
DOMText

Keep in mind that DOMNodelists are "live" - changes to the document or node that the DOMNodelist was derived from will be reflected in the DOMNodelist. In other words, a list of a parent node's children will change if you change the parent's children!

It seems that with zend.ze1_compatibility_mode on, the only way to iterate over the items list is with :
for ($i = 0; $i < $nodeList->length; ++$i) {
    $nodeName = $nodeList->item($i)->nodeName;
    $nodeValue = $nodeList->item($i)->nodeValue;
}

As other attemps failed :

for ($i = 0; $i < $nodeList->length; ++$i) {
    $node = &$nodeList->item($i);
    $nodeName = $node->nodeName;
    $nodeValue = $node->nodeValue;
}

or :
foreach ($nodeList as $node) {
    echo $node->nodeName;
    echo $node->nodeValue;
}

tfg_allardyce at gmail dot com

I have had exactly this problem.

To rectify I've had to do this:
<?php
$old_element = $doc->getElementsByTagName('Element1')->item(0);
$new_element = $doc->createElement('NewElement1');

$old_element_childNodes = $old_element->childNodes;
$length = $old_element_childNodes->length;

for($i = 0; $i < $length; $i++)
{        
    $oldChildren_array[] = $old_element_childNodes->item($i);
}

foreach($oldChildren_array as $old_c)
{
    $new_element->appendChild($old_c);
}
?>

Rather than this:
(which I will bug report)
<?php
$old_element = $doc->getElementsByTagName('Element1')->item(0):
$new_element = $doc->createElement('NewElement1');

foreach($old_element->childNode as $node)
{
     $new_element->appendChild($node);
}

?>

Using the latter, randomally removes the children!

NodeList are something annoying because you can't output the content with a simple print_r, so I did a little function that add all the node to a new empty DOMDocument and output it as a string.
Have fun.

<?php

public function domNodeList_to_string($DomNodeList) {
    $output = '';
    $doc = new DOMDocument;
    while ( $node = $DomNodeList->item($i) ) {
        // import node
        $domNode = $doc->importNode($node, true);
        // append node
        $doc->appendChild($domNode);
        $i++;
    }
    $output = $doc->saveXML();
    $output = print_r($output, 1);
    // I added this because xml output and ajax do not like each others
    $output = htmlspecialchars($output);
    return $output;
}

?>