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DOMXPath::registerPhpFunctions

PHP function Edit on GitHub ✎

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

Description

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

Void

Errors/Exceptions

Throws a ValueError if a callback name is not valid.
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 `callable`s for callbacks when using `restrict` with `array` entries.

Examples

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

book.xml

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>

DOMXPath::registerPhpFunctions with php:functionString

php

<?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:

output

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

DOMXPath::registerPhpFunctions with php:function

php

<?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:

output

Books with multiple authors:
PHP Basics

DOMXPath::registerPhpFunctions with a callable

php

<?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:

output

Books with multiple authors:
PHP Basics

DOMXPath::registerPhpFunctions

Description

Parameters

Return Values

Errors/Exceptions

Changelog

Examples

See Also