Enables the ability to use PHP functions as XSLT functions

# XSLTProcessor::registerPHPFunctions

(PHP 5 >= 5.0.4, PHP 7, PHP 8)

XSLTProcessor::registerPHPFunctions — Enables the ability to use PHP functions as XSLT functions

### Description

public XSLTProcessor::registerPHPFunctions(array|string|null `$functions` = `null`): void

This method enables the ability to use PHP functions as XSLT functions within XSL stylesheets.

### Parameters

`functions`

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

  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.

### 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.

### Return Values

No value is returned.

### 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 `functions` with array entries.

### Examples

Example #1 Simple PHP Function call from a stylesheet

`<?php
$xml = <<<EOB
<allusers>
<user>
<uid>bob</uid>
</user>
<user>
<uid>joe</uid>
</user>
</allusers>
EOB;
$xsl = <<<EOB
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:php="http://php.net/xsl">
<xsl:output method="html" encoding="utf-8" indent="yes"/>
<xsl:template match="allusers">
<html><body>
<h2>Users</h2>
<table>
<xsl:for-each select="user">
<tr><td>
<xsl:value-of
select="php:function('ucfirst',string(uid))"/>
</td></tr>
</xsl:for-each>
</table>
</body></html>
</xsl:template>
</xsl:stylesheet>
EOB;
$xmldoc = new DOMDocument();
$xmldoc->loadXML($xml);
$xsldoc = new DOMDocument();
$xsldoc->loadXML($xsl);
$proc = new XSLTProcessor();
$proc->registerPHPFunctions();
$proc->importStyleSheet($xsldoc);
echo $proc->transformToXML($xmldoc);
?>`

### See Also

- DOMXPath::registerPhpFunctions() - Register PHP functions as XPath functions

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