xpath: getting child node by searching parent attribute - php

Question

I have a KML file for google maps that I want to edit. Here's a stripped-down version:
<?xml version='1.0' encoding='UTF-8'?>
<kml xmlns='http://www.opengis.net/kml/2.2'>
<Document>
<Placemark>
<name>00</name>
<snippet></snippet>
<description><![CDATA[]]></description>
<styleUrl>#Style0-polygon-3-map</styleUrl>
<ExtendedData>
<Data name='Two-Digit Districts'>
<value>AK-00</value>
</Data>
<Data name='Standard Districts'>
<value>AK-AL</value>
</Data>
<Data name='At Large as District 1'>
<value>AK-1</value>
</Data>
<Data name='Full District Name'>
<value>Alaska At Large</value>
</Data>
<Data name=''>
<value>AK</value>
</Data>
</ExtendedData>
</PlaceMark>
</Document>
</kml>
In my php code, I'm digging into each placemark node using SimpleXML:
foreach ($kml->Document->Placemark as $placemark) {
$extendeddata = $placemark->ExtendedData;
}
I need to get the <Data> node where the name attribute matches "At Large as District 1". In the XML tools plugin for NPP, when I take just the <ExtendedData>...</ExtendedData> node, this query returns the node I want: //Data[#name='At Large as District 1']. However, when I try that same query in PHP:
$targetnode = $extendeddata->xpath("//Data[#name='At Large as District 1']")
I get an empty array. I don't understand why what should be a perfectly valid xpath query isn't returning any information. Am I missing something?

Answer 1

There is an ending tag mismatch.
Replace </PlaceMark> with </Placemark>
Code
You have to register with a namespace in order to do an xpath in this case.
$extendeddata = simplexml_load_string( $str );
$extendeddata->registerXPathNamespace( 'ns', 'http://www.opengis.net/kml/2.2' );
$targetnode = $extendeddata->xpath("//ns:Data[#name='At Large as District 1']");
Output
Array
(
[0] => SimpleXMLElement Object
(
[#attributes] => Array
(
[name] => At Large as District 1
)
[value] => AK-1
)
)
Hope this helps.