DOM-XML: get Elements with namespaceprefix

[Susanne Klemm]

Hello!

I am working with the XML-DOM-Extension. I want to change the content of a
variable in a XSL-Document. The following testscript works well.
$dom = domxml_open_file(getcwd()."/einzelnes_item.xsl")
$elements = $dom->get_elements_by_tagname("table")
echo count($elements)." Elements<br/>";
for ($i=0;$i<count($elements);$i++)
{
$element = $elements[$i];
echo " Tagname: ".$element->tagname();
$border = $element->get_attribute("border");
echo " border: ".$border."<br>";
}

But if I try to use $elements =
$dom->get_elements_by_tagname("xsl:variable") I get an array with one
element (even if there are more variables) and the rest of the code doesn't
work at all. When I call a funtion of $element I get an error:
Fatal error: Call to a member function on a non-object.

Do I not can use namespacesprefixes? Or did I made a mistake?

TIA

Susanne