php-doc-en/reference/dom/functions/dom-domxpath-evaluate.xml

<?xml version="1.0" encoding="iso-8859-1"?>
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<refentry id="function.dom-domxpath-evaluate">
 <refnamediv>
  <refname>DOMXPath->evaluate()</refname>
  <refpurpose>
   Evaluates the given XPath expression and returns a typed result if possible.
  </refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <classsynopsis>
   <ooclass><classname>DOMXPath</classname></ooclass>
   <methodsynopsis>
    <type>mixed</type>
    <methodname>evaluate</methodname>
    <methodparam><type>string</type><parameter>expression</parameter></methodparam>
    <methodparam choice="opt"><type>DOMNode</type><parameter>contextnode</parameter></methodparam>      
   </methodsynopsis>
  </classsynopsis>
  <para>
   Executes the given XPath <parameter>expression</parameter> and returns
   a typed result if possible.
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>expression</parameter></term>
     <listitem>
      <para>
       The XPath expression to execute.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>contextnode</parameter></term>
     <listitem>
      <para>
       The optional <parameter>contextnode</parameter> can be specified for
       doing relative XPath queries. By default, the queries are relative to 
       the root element.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns a typed result if possible or a <classname>DOMNodeList</classname> 
   containing all nodes matching the given XPath <parameter>expression</parameter>. 
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>Getting the count of all the english books</title>
    <programlisting role="php">
<![CDATA[
<?php

$doc = new DOMDocument;

$doc->load('book.xml');

$xpath = new DOMXPath($doc);

$tbody = $doc->getElementsByTagName('tbody')->item(0);

// our query is relative to the tbody node
$query = 'count(row/entry[. = "en"])';

$entries = $xpath->evaluate($query, $tbody);
echo "There are $entries english books\n";

?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
There are 2 english books
]]>
    </screen>
   </example>
  </para>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><xref linkend="function.dom-domxpath-query" /></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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