Description:
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hi, why not extend DOM classes with addEventListener and removeEventListener methods. In php they are useful as observer pattern

the propagation with two models (capturing / bubbling)
http://www.quirksmode.org/js/events_order.html

mutation events in dom3 events:
http://www.w3.org/TR/DOM-Level-3-Events/#events-mutationevents
http://www.w3.org/TR/DOM-Level-3-Events/#events-mutationnameevents

for example i can monitor a subtree with

$mysel->addEventListener("DOMSubtreeModified", array($this,'mycallback'), false);

public function mycallback($event)
{
      echo "subtree changed at " . (string)$event->relatedNodeArg;
}

list of events:

DOMSubtreeModified
DOMNodeInserted
DOMNodeRemoved
DOMNodeRemovedFromDocument
DOMNodeInsertedIntoDocument
DOMAttrModified
DOMElementNameChanged
DOMCharacterDataModified
DOMElementNameChanged
DOMAttributeNameChanged

thank you