Tim Knip's Log

July 24, 2004

Validating XML with PHP using catalogs (on win32)

Problem: I had some XHTML-strict files which needed to be validated using PHP:

sample.html:



<!DOCTYPE html 

     PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"

     "DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">

  <head>

    <title>XHTML validatation test</title>

  </head>

  <body>

    <p>Hello World</p>

  </body>

</html>

Now, in PHP we can use DOMXML as follows:



<?php

  $domxml = domxml_open_file('sample.html');

  if(is_object($domxml))

  {

    $error = array();

    if($domxml->validate($error))

    {

      echo 'this file is valid!';

    }

  }

?>

But! Aaargh... PHP is now gonna download the DTD from http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd !!! Takes ages!
No, i want to validate against a local dtd!.

Luckily came across this interesting piece. It describes the usage of XML-Catalogs with PHP. Such a catalog redirects for example 'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd' to a DTD stored locally. PHP's DOMXML is build using GNome's libxml so we can use a catalog.

Steps for using XML Catalog with PHP on win32/IIS:
1] download the necessary XHTML 1.0 DTD's here
2] extract the zip into root of IIS (ie: C:\Inetpub\wwwroot)
3] create 'catalog.xml' in for example 'C:\Inetpub\wwwroot':

<?xml version="1.0"?>
<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 
	"http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd">
<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">
<public publicId="-//W3C//DTD XHTML 1.0 Strict//EN" uri="xhtml1/xhtml1-20020801/DTD/xhtml1-strict.dtd" />
</catalog>

Finally:
4] set up a system environment variable 'XML_CATALOG_FILES' with value '<path-to-catalog.xml>

That's it! Now you can validate your xml agains locally stored DTD's!

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