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<refentry xml:id="domxpath.registerphpfunctions" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>DOMXPath::registerPhpFunctions</refname>
  <refpurpose>Register PHP functions as XPath functions</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis role="DOMXPath">
   <modifier>public</modifier> <type>void</type><methodname>DOMXPath::registerPhpFunctions</methodname>
   <methodparam choice="opt"><type class="union"><type>string</type><type>array</type><type>null</type></type><parameter>restrict</parameter><initializer>&null;</initializer></methodparam>
  </methodsynopsis>
  <para>
   This method enables the ability to use PHP functions within XPath expressions.
  </para>

 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>restrict</parameter></term>
     <listitem>
      <para>
       Use this parameter to only allow certain functions to be called from XPath.
      </para>
      <para>
       This parameter can be one of the following:
       a <type>string</type> (a function name),
       an indexed <type>array</type> of function names,
       or an associative <type>array</type> with keys being the function name
       and the associated value being the <type>callable</type>.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.void;
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry>8.4.0</entry>
      <entry>
       It is now possible to use <type>callable</type>s for callbacks
       when using <parameter>restrict</parameter> with <type>array</type>
       entries.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   The following examples use <filename>book.xml</filename> which contains the following:
  </para>
  <para>
   <example>
    <title>book.xml</title>
    <programlisting role="xml">
<![CDATA[
<?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>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   <example>
    <title><methodname>DOMXPath::registerPHPFunctions</methodname> with <literal>php:functionString</literal></title>
    <programlisting role="php">
<![CDATA[
<?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";
}

?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
Found 2 books starting with 'PHP':
PHP Basics by Jim Smith
PHP Secrets by Jenny Smythe
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title><methodname>DOMXPath::registerPHPFunctions</methodname> with <literal>php:function</literal></title>
    <programlisting role="php">
<![CDATA[
<?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";
}

?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
Books with multiple authors:
PHP Basics
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title><methodname>DOMXPath::registerPHPFunctions</methodname> with a <type>callable</type></title>
    <programlisting role="php">
<![CDATA[
<?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";
}

?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
Books with multiple authors:
PHP Basics
]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><methodname>DOMXPath::registerNamespace</methodname></member>
    <member><methodname>DOMXPath::query</methodname></member>
    <member><methodname>DOMXPath::evaluate</methodname></member>
    <member><methodname>XSLTProcessor::registerPHPFunctions</methodname></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>
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