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Asked: 2026-06-11T00:17:43+00:00

Possible Duplicate: Simplify PHP DOM XML parsing – how? Here is my XML (c.xml):

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Possible Duplicate:
Simplify PHP DOM XML parsing – how?

Here is my XML (c.xml):

<?xml version="1.0" encoding="utf-8"?>
<root>
    <head>
        <title id="title">Hello</title>
    </head>
</root>

What I do:

$dom = new DOMDocument;

$dom->load('./c.xml');

var_dump($dom->getElementById('title'));die(); // returns NULL

What is the problem here&?

UPD

$dom->validate(); returns DOMDocument::validate(): no DTD found!

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1 Answer

  1. Editorial Team

    I think The Manual explains why this may happen

    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.

    Potential fixes:

    1. Call $dom->validate();, afterwards you can use $dom->getElementById(), regardless of the errors for some reason.

    2. Use XPath if you don’t feel like validating:

      $x = new DOMXPath($dom);

      $el = $x->query("//*[@id='title']")->item(0); //Look for id=title

    Example of using a custom DTD:

    $dtd = '<!ELEMENT note (to,from,heading,body)>
        <!ELEMENT to (#PCDATA)>
        <!ELEMENT from (#PCDATA)>
        <!ELEMENT heading (#PCDATA)>
        <!ELEMENT body (#PCDATA)>';

$systemId = 'data://text/plain;base64,'.base64_encode($dtd);

$creator = new DOMImplementation;
$doctype = $creator->createDocumentType($root, null, $systemId); //Based on your DTD from above
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