PHP SoapClient: set a namespace without prefix

php xml soap wsdl

PHP Snippet 1:

$document = new DOMDocument();
$document->loadXML(
    '<foo xmlns="WebApplicationImport"/>'
);

PHP Snippet 2:

Notice: DOMDocument::loadXML(): xmlns: URI WebApplicationImport is not absolute in Entity

PHP Snippet 3:

soapHeader = new SOAPHeaderElement("", "HeaderElementName");

soapHeader.addAttribute("", "xmlns", "url");