php-doc-en/reference/dom/domdocument/getelementbyid.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="domdocument.getelementbyid" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>DOMDocument::getElementById</refname>
  <refpurpose>Searches for an element with a certain id</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <modifier>public</modifier> <type>DOMElement</type><methodname>DOMDocument::getElementById</methodname>
   <methodparam><type>string</type><parameter>elementId</parameter></methodparam>
  </methodsynopsis>
  <para>
   This function is similar to
   <xref linkend="domdocument.getelementsbytagname" /> but 
   searches for an element with a given id.
  </para>
  <para>
   For this function to work, you will need either to set some ID attributes
   with <xref linkend="domelement.setidattribute" />
   or a DTD which defines an attribute to be of type ID. 
   In the later case, you will need to validate your document with
   <xref linkend="domdocument.validate" /> 
   or <link
       linkend="domdocument.props.validateonparse">DOMDocument::$validateOnParse</link> before using this function.
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>elementId</parameter></term>
     <listitem>
      <para>
       The unique id value for an element.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the <classname>DOMElement</classname> or &null; if the element is
   not found. 
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <example>
   <title>DOMDocument::getElementById() Example</title>
   &dom.book.example;
   <programlisting role="php">
<![CDATA[
<?php

$doc = new DomDocument;

// We need to validate our document before refering to the id
$doc->validateOnParse = true;
$doc->Load('book.xml');

echo "The element whose id is 'php-basics' is: " . $doc->getElementById('php-basics')->tagName . "\n";

?>
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
The element whose id is 'php-basics' is: book 
]]>
   </screen>
  </example>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><methodname>DOMDocument::getElementsByTagName</methodname></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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