PHP Conference Japan 2024

DOMXPath::registerPhpFunctions

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

DOMXPath::registerPhpFunctionsRegister PHP functions as XPath functions

Description

public 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.

Changelog

Version Description
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('book.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('book.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('book.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

See Also

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