If you want to recurse over a DOM then this might help: 
<?php 

/**
 * PHP's DOM classes are recursive but don't provide an implementation of 
 * RecursiveIterator. This class provides a RecursiveIterator for looping over DOMNodeList
 */
class DOMNodeRecursiveIterator extends ArrayIterator implements RecursiveIterator {
  
  public function __construct (DOMNodeList $node_list) {
    
    $nodes = array();
    foreach($node_list as $node) {
      $nodes[] = $node;
    }
    
    parent::__construct($nodes);
    
  }
  
  public function getRecursiveIterator(){
    return new RecursiveIteratorIterator($this, RecursiveIteratorIterator::SELF_FIRST);
  }
  
  public function hasChildren () {
    return $this->current()->hasChildNodes();
  }

  
  public function getChildren () {
    return new self($this->current()->childNodes);
  }
  
}
?>

In PHP 5.2.5 (Windows) it is not possible to iterate correctly over the DOMNodeList object returned by DOMNode->childNodes using foreach. Instead I had to use the for loop in conjunction with the item() method of DOMNodeList for iterating over all child nodes correctly.

I don't know whether this is really a bug, but apparently it is.

It's worth to mention that DOMNodeList is not an Array,  so you have to convert first to an array before to use for, foreach or array_map, array_filter, array_walk functions.

Use iterator_to_array to make the conversion ( since PHP 5.1.0 ) .

<code>
  /* @ suppress warning var_dump not yet implemented for class */

@array_walk( iterator_to_array( $Some_NodeList ), 'var_dump' ) );

foreach( iterator_to_array( $Some_NodeList ) as $node )
    @var_dump( $node );

</code>

Hope is usefull.

Note that $length is calculated (php5.3.2).
Iterating over a large NodeList may be time expensive.

Prefer :
$nb = $nodelist->length;
for($pos=0; $pos<$nb; $pos++)

Than:
for($pos=0; $pos<$nodelist->length; $pos++)

I had a hard time figuring that out...

You can modify, and even delete, nodes from a DOMNodeList if you iterate backwards:

$els = $document->getElementsByTagName('input');
for ($i = $els->length; --$i >= 0; ) {
  $el = $els->item($i);
  switch ($el->getAttribute('name')) {
    case 'MAX_FILE_SIZE' :
      $el->parentNode->removeChild($el);
    break;
    case 'inputfile' :
      $el->setAttribute('type', 'text');
    //break;
  }
}

I have done some testing and have found 2 results:
(My System: Win XP with PHP 5.2.1)

1) Iteration with foreach does function correctly as "james dot j dot hackett at gmail dot com" writes, _if_ you only do readonly stuff with foreach or minor writings of some attributes.

2) foreach does not function, if you are doing some DOM-Operations while iterating. In my situation it was adding the iterated $node as an child to an new node:

$newNode = $dom->createElement('newNode') ;
foreach ($nodeList as $node) {
  echo $node->nodeValue ;
  $newNode->appendChild($node) ;
}

This only gives you the first element ...

I'm interpreting it as an confusing but correct behavior because of the changes within the $dom-object while appending the node at an additional place ... 

So, if you want to do something like 2) use for, length and item() :)

In Response to 'kassah at gmail'

You don't need to convert a DOMNodeList to an array in order iterate through it using 'foreach'.  You can use foreach directly with the DOMNodeList.

$nodeList = $someDomDocument->getElementsbytagname('user');

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

That's actually incorrect. You can use function results as objects. It makes building an API for your database very clean and neat. For example:

Our code:

$articles = Node::screate('tags', 123456)->assets('like:title:test')->articles;

We use the above code to get articles that are linked to assets that are linked to a specific tag in our database.

Addition to my first note:

An traditional for-loop does not allow you to change the DOM-tree while looping - the effects are the nearly the same as with foreach. So you have to collect the nodes in an array and do the tree-altering stuff within a second loop (looping the array this time ...)