This method was designed specifically for DOMNode based classes only. 
changing to feature request and I will consider and evaluate expanding 
its functionality.

This would be very nice!

this would be really helpful!

very helpfull, extending DOMNode's almost implies it, pls hurry, ty

Any movement on this? The method should probably be called registerNodeListClass

I’d like to provide a valid use-case for this bug.

I have created an extended DOMDocument that upon __construct also creates an  XPath object, that way I can add methods to DOMElement to allow for DOMElement->xpath ('...') instead of using DOMXPath->query ('...', DOMNode). This makes the DOM more chainable and simpler to use without so many temporary variables.

What I want to do is extend DOMNodeList so that one function call can apply to all nodes returned from an XPath query, e.g.

DOMNode->xpath ('a')->addClass ('link');

Is anybody aware of any other work around that can be used to achieve this same effect?

@kroccamen While not that elegant, you can create a decorator to solve this issue. Here's a template to use:

    class MyDomElement extends DOMElement {
      function xpath($query) {
        return new DomNodeListDecorator($this->ownerDocument->getXpathSelector()-
>query($query, $this));
      }
    }

    class DomNodeListDecorator implements IteratorAggregate {
      protected $nodeList;

      function __construct($nodeList) {
        $this->nodeList = $nodeList;
      }

      function getIterator() {
        return $this->nodeList;
      }

      function __get($name) {
        if ($name == 'length') {
          return $this->nodeList->length;
        }
        throw new Exception("Undefined attribute {$name}");
      }

      function item($index) {
        return $this->nodeList->item($index);
      }
    }