XML access to a "default" attribute

Just curious how to obtain the information from "startTime" of this xml document using php and simplexml

<event xmlns="http开发者_运维知识库://schemas.google.com/contact/2008" xmlns:default="http://schemas.google.com/g/2005" rel="anniversary">
    <default:when xmlns="http://schemas.google.com/g/2005" startTime="2009-05-09"/>
  </event>

My initial thought was.

$xml->event->default['startTime']

OR

$xml->event->when['startTime']

But both return NULL... when I can see the data isn't NULL. Any thoughts on how to obtain this information?

Well after much more research I found this as a result and is working perfectly.

//    Get All Events
foreach ($xml->event as $e) {
    $defaults = $e->children('http://schemas.google.com/g/2005'); 

    if($e['rel'] == "anniversary") {
        $obj->anniversary = (string) $defaults->when->attributes()->startTime;
    }
}