XML DOM function?

[mshen]

I have a structure like
<chart>
<Textbox>
<Text>Demo</Text>
</Textbox>
</chart>

Please show me how to do with PHP and XMLDOM if I want to change the word "Demo" with "Test".

I read the PHP help file but it doesn,t tell me how to use xml dom functions.

Thanks a lot.

[mshen]

I try DOM like the code here:

<?php

if(!$dom = domxml_open_file("test.xml")) {
echo "Error while parsing the document\n";
exit;
}

$root = $dom->document_element();
$elements = $dom->get_elements_by_tagname("Text");
//echo count($elements);
echo $elements[0]->tagname;
echo $elements[0];
//echo "ok";
?>

It works,but the problem is how to display the element value and chang it.

Please give me the function name and how to use it if you know.Thanks.