title: SimpleXmlElement and XPath, getting empty array()
body: <p>I am having a little trouble with parsing XML from a google checkout response.  The XML is coming straight from the google server so there is no problem with the XML itself.</p>
  
  <p>I want to get hold of all the new-order-notification tags</p>
  
  <p>I tried this but get an empty array() returned everytime.</p>
  
  <pre><code>$xml = new SimpleXmlElement($raw_xml);
  $notifications = $xml-&gt;xpath('notifications');
  $notifications = $xml-&gt;xpath('/notification-history-response/notifications/new-order-notification');
  $notifications = $xml-&gt;xpath('//new-order-notification');
  </code></pre>
  
  <p>An XML snipet (Just the beginning)
  </p>
  
  <pre><code>&lt;notification-history-response xmlns="http://checkout.google.com/schema/2" serial-number="c5cda190-0eb1-4f91-87cd-e656e5598d38"&gt;
    &lt;notifications&gt;
      &lt;new-order-notification serial-number="271578974677716-00001-7"&gt;
        &lt;buyer-billing-address&gt;
          &lt;address1&gt;19 sandbox st&lt;/address1&gt;
          &lt;address2&gt;&lt;/address2&gt;
  </code></pre>