php - xPath finds nothing but *

Question

This is starting to piss me off real bad. I have this XML code:

Updated with correct namespaces

<?xml version="1.0" encoding="utf-8"?>

<Infringement xsi:schemaLocation="http://www.movielabs.com/ACNS http://www.movielabs.com/ACNS/ACNS2v1.xsd" xmlns="http://www.movielabs.com/ACNS" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Case>
    <ID>...</ID>
    <Status>Open</Status>
  </Case>
  <Complainant>
    <Entity>...</Entity>
    <Contact>...</Contact>
    <Address>...</Address>
    <Phone>...</Phone>
    <Email>...</Email>
  </Complainant>
  <Service_Provider>
    <Entity>...</Entity>
    <Address></Address>
    <Email>...</Email>
  </Service_Provider>
  <Source>
    <TimeStamp>...</TimeStamp>
    <IP_Address>...</IP_Address>
    <Port>...</Port>
    <DNS_Name></DNS_Name>
    <Type>...</Type>
    <UserName></UserName>
    <Number_Files>1</Number_Files>
    <Deja_Vu>No</Deja_Vu>
  </Source>
  <Content>
    <Item>
      <TimeStamp>...</TimeStamp>
      <Title>...</Title>
      <FileName>...</FileName>
      <FileSize>...</FileSize>
      <URL></URL>
    </Item>
  </Content>
</Infringement>

And this PHP code:

<?php 
    $data = urldecode($_POST["xml"]);
    $newXML = simplexml_load_string($data);

    var_dump($newXML->xpath("//ID"));
?>

I've dumped only $newXML and gotten tons of data, but the only xPath I've run that returned anything but an empty array was "*"

Isn't "//ID" supposed to find all ID nodes in the document? Why isn't it working?

Thanks

Answer 1

Your XML document's root element seems to have default namespace with URI "http://www.movielabs.com/ACNS". This means that all elements in your document belong to that namespace. The problem is that all XPath expressions that do not have a namespace prefix are searching for elements that don't belong to any namespace. To search for elements (or attributes...) from a certain namespace you need to register the namespace URI to some prefix and then use this prefix in your XPath expression.

In case of PHP's simpleXML it's done something like this

$newXML = simplexml_load_string($data);
$newXML->registerXPathNamespace('prefix', 'http://www.movielabs.com/ACNS');
var_dump($newXML->xpath("//prefix:ID"));

prefixcan be practically any text, but the namespace URI must match exactly the one used in your XML document.