Ben domxml_new_doc kullanarak çıkış xml çalışıyorum.

However, I just got the call to undefined function domxml_new_doc() error. I tried google it but still not luck. Do I have to install any extension or library? Thanks for the help.

 $doc=domxml_new_doc("1.0"); //error on this line....
$node=$doc->create_element("marker");
$parnode=$doc->append_child($node);