(PHP 5)
DOMDocument::getElementById — Searches for an element with a certain id
This function is similar to DOMDocument::getElementsByTagName but searches for an element with a given id.
For this function to work, you will need either to set some ID attributes with 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 DOMDocument::validate or DOMDocument::$validateOnParse before using this function.
elementIdThe unique id value for an element.
Returns the DOMElement or NULL if the element is
not found.
Example #1 DOMDocument::getElementById() Example
以下范例使用了 book.xml，其内容如下：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE books [
<!ELEMENT books (book+)>
<!ELEMENT book (title, author+, xhtml:blurb?)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT blurb (#PCDATA)>
<!ELEMENT author (#PCDATA)>
<!ATTLIST books xmlns CDATA #IMPLIED>
<!ATTLIST books xmlns:xhtml CDATA #IMPLIED>
<!ATTLIST book id ID #IMPLIED>
<!ATTLIST author email CDATA #IMPLIED>
]>
<?xml-stylesheet type="text/xsl" href="style.xsl"?>
<books xmlns="http://books.php/" xmlns:xhtml="http://www.w3.org/1999/xhtml">
<book id="php-basics">
<title>PHP Basics</title>
<author email="[email protected]">Jim Smith</author>
<author email="[email protected]">Jane Smith</author>
<xhtml:blurb><![CDATA[
<p><em>PHP Basics</em> provides an introduction to PHP.</p>
]]></xhtml:blurb>
</book>
<book id="php-advanced">
<title>PHP Advanced Programming</title>
<author email="[email protected]">Jon Doe</author>
</book>
</books>
<?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";
?>
以上例程会输出：
The element whose id is 'php-basics' is: book