Error when using PHP5

Fatal error: Call to undefined method DOMElement::first_child() in E:\DomZeus\sitebuddycom\wwwroot\modules\amazontools\amazon.php5.inc on line 111

The php site says:
"This extension has been moved to the PECL repository and is no longer bundled with PHP as of PHP 5.0.0.'

The PERL repository http://pecl.php.net/package/domxml says:
"This extension allows you to operate on an XML document with the DOM API. It has been superseded by the DOM extension that ships with PHP 5.
Although it should be possible to use this old domxml extension with PHP 5, its use is highly discouraged, as there a very high potential for conflicts with the new dom extension.

If you are migrating from PHP 4 to PHP 5, the recommended best-practice is to port your domxml code to the much better dom code."

Also for PHP5 no distribusion: "If you really must build domxml, you will need to obtain the sources from CVS and build them yourself."

Thanks for this great module,
Christophe D