PHP simplexml: why does xpath stop working?

Question

A strange thing happened after a supplier changed the XML header a bit. I used to be able to read stuff using xpath, but now I can\'t even get a reply with

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Answer 1

Most likely this is because they've introduced a default namespace (xmlns="http://iptc.org/std/NewsML/2003-10-10/") into their document. SimpleXML's support for default namespaces is not very good, to put it mildly.

Can you try to explicitly register a namespace prefix:

$xml->registerXPathNamespace("n", "http://iptc.org/std/NewsML/2003-10-10/");
$xml->xpath('/n:NewsML');

You would have to adapt your XPath expressions to use the "n:" prefix on every element. Here is some additional info: http://people.ischool.berkeley.edu/~felix/xml/php-and-xmlns.html.

EDIT: As per the spec:

The registerXPathNamespace() function creates a prefix/ns context for the next XPath query.

This means it would have to be called before every XPath query, thus a function to wrap XPath queries would be the natural thing to do:

function simplexml_xpath_ns($element, $xpath, $xmlns)
{
    foreach ($xmlns as $prefix_uri)
    {
        list($prefix, $uri) = explode("=", $prefix_uri, 2);
        $element->registerXPathNamespace($prefix, $uri);
    }
    return $element->xpath($xpath);
}

Usage:

$xmlns = ["n=http://iptc.org/std/NewsML/2003-10-10/"];
$result = simplexml_xpath_ns($xml, '/n:NewsML', $xmlns);