(PHP 5 >= 5.1.0, PHP 7, PHP 8)
SimpleXMLElement::registerXPathNamespace — Creates a prefix/ns context for the next XPath query
Creates a prefix/ns context for the next XPath query. In particular, this is
helpful if the provider of the given XML document alters the namespace
prefixes. registerXPathNamespace will create a prefix for
the associated namespace, allowing one to access nodes in that namespace
without the need to change code to allow for the new prefixes dictated by the
provider.
prefix
The namespace prefix to use in the XPath query for the namespace given in
namespace.
namespace
The namespace to use for the XPath query. This must match a namespace in
use by the XML document or the XPath query using
prefix will not return any results.
示例 #1 Setting a namespace prefix to use in an XPath query
<?php
$xml = <<<EOD
<book xmlns:chap="http://example.org/chapter-title">
<title>My Book</title>
<chapter id="1">
<chap:title>Chapter 1</chap:title>
<para>Donec velit. Nullam eget tellus vitae tortor gravida scelerisque.
In orci lorem, cursus imperdiet, ultricies non, hendrerit et, orci.
Nulla facilisi. Nullam velit nisl, laoreet id, condimentum ut,
ultricies id, mauris.</para>
</chapter>
<chapter id="2">
<chap:title>Chapter 2</chap:title>
<para>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Proin
gravida. Phasellus tincidunt massa vel urna. Proin adipiscing quam
vitae odio. Sed dictum. Ut tincidunt lorem ac lorem. Duis eros
tellus, pharetra id, faucibus eu, dapibus dictum, odio.</para>
</chapter>
</book>
EOD;
$sxe = new SimpleXMLElement($xml);
$sxe->registerXPathNamespace('c', 'http://example.org/chapter-title');
$result = $sxe->xpath('//c:title');
foreach ($result as $title) {
echo $title . "\n";
}
?>以上示例会输出：
Chapter 1 Chapter 2
Notice how the XML document shown in the example sets a namespace with a
prefix of chap. Imagine that this document (or another
one like it) may have used a prefix of c in the past for
the same namespace. Since it has changed, the XPath query will no longer
return the proper results and the query will require modification. Using
registerXPathNamespace avoids future modification of the
query even if the provider changes the namespace prefix.
Looks like you have to use registerXPathNamespace for each node when using XPath:
<?php
$xml = simplexml_load_file($filename);
$xml->registerXPathNamespace('test', 'http://example.com');
$shopping_element = $xml->xpath('test:shopping-list');
// Breaks with out the following line:
$shopping_element->registerXPathNamespace('test', 'http://example.com');
$fruit = $shopping_element->xpath('test:fruit');
?>