PHP Manual: DOMXPath::registerPhpFunctions

Description

public function DOMXPath::registerPhpFunctions(string|array|null $restrict = null): void

This method enables the ability to use PHP functions within XPath expressions.

Parameters

restrict

Use this parameter to only allow certain functions to be called from XPath.

This parameter can be one of the following: a string (a function name), an indexed array of function names, or an associative array with keys being the function name and the associated value being the callable.

Return Values

No value is returned.

Errors/Exceptions

Throws a ValueError if a callback name is not valid.
Throws a ValueError if options contains an invalid option.
Throws a ValueError if overrideEncoding is an unknown encoding.
Throws a TypeError if a given callback is not callable.

Changelog

Version	Description
8.4.0	Invalid callback names now throws a ValueError. Passing a non-callable entry now throws a TypeError.
8.4.0	It is now possible to use callables for callbacks when using `restrict` with array entries.

Examples

The following examples use book.xml which contains the following:

Example #1 book.xml

<?xml version="1.0" encoding="UTF-8"?>
<books>
 <book>
  <title>PHP Basics</title>
  <author>Jim Smith</author>
  <author>Jane Smith</author>
 </book>
 <book>
  <title>PHP Secrets</title>
  <author>Jenny Smythe</author>
 </book>
 <book>
  <title>XML basics</title>
  <author>Joe Black</author>
 </book>
</books>

Example #2 DOMXPath::registerPhpFunctions() with php:functionString

<?php
$doc = new DOMDocument;
$doc->load('examples/book-simple.xml');

$xpath = new DOMXPath($doc);

// Register the php: namespace (required)
$xpath->registerNamespace("php", "http://php.net/xpath");

// Register PHP functions (no restrictions)
$xpath->registerPhpFunctions();

// Call substr function on the book title
$nodes = $xpath->query('//book[php:functionString("substr", title, 0, 3) = "PHP"]');

echo "Found {$nodes->length} books starting with 'PHP':\n";
foreach ($nodes as $node) {
    $title  = $node->getElementsByTagName("title")->item(0)->nodeValue;
    $author = $node->getElementsByTagName("author")->item(0)->nodeValue;
    echo "$title by $author\n";
}

?>

The above example will output something similar to:

Found 2 books starting with 'PHP':
PHP Basics by Jim Smith
PHP Secrets by Jenny Smythe

Example #3 DOMXPath::registerPhpFunctions() with php:function

<?php
$doc = new DOMDocument;
$doc->load('examples/book-simple.xml');

$xpath = new DOMXPath($doc);

// Register the php: namespace (required)
$xpath->registerNamespace("php", "http://php.net/xpath");

// Register PHP functions (has_multiple only)
$xpath->registerPhpFunctions("has_multiple");
 
function has_multiple($nodes) {
    // Return true if more than one author
    return count($nodes) > 1;
}
// Filter books with multiple authors
$books = $xpath->query('//book[php:function("has_multiple", author)]');

echo "Books with multiple authors:\n";
foreach ($books as $book) {
    echo $book->getElementsByTagName("title")->item(0)->nodeValue . "\n";
}

?>

The above example will output something similar to:

Books with multiple authors:
PHP Basics

Example #4 DOMXPath::registerPhpFunctions() with a callable

<?php
$doc = new DOMDocument;
$doc->load('examples/book-simple.xml');

$xpath = new DOMXPath($doc);

// Register the php: namespace (required)
$xpath->registerNamespace("php", "http://php.net/xpath");

// Register PHP functions (has_multiple only)
$xpath->registerPhpFunctions(["has_multiple" => fn ($nodes) => count($nodes) > 1]);

// Filter books with multiple authors
$books = $xpath->query('//book[php:function("has_multiple", author)]');

echo "Books with multiple authors:\n";
foreach ($books as $book) {
    echo $book->getElementsByTagName("title")->item(0)->nodeValue . "\n";
}

?>

The above example will output something similar to:

Books with multiple authors:
PHP Basics

DOMXPath::registerPhpFunctions

Description

Parameters

Return Values

Errors/Exceptions

Changelog

Examples

See Also