PHP SOAP lib AuthenticationManager parameter UserInformation

Dear Commuinity,

i was wondering anyone could help me out getting a valid Request (XML) from my SOAPUI Webservice.
How should i send User and Passwort Parameters via PHP SOAP lib to the Webservice?

The example __call is sendCompany
Aren't the parameters for Userinformation completle wrong? Have already tried more variations like Userinformation, User, loginetc.

My PHP code:

<?php
$option=array('trace'=>1);
$soapClient = new SoapClient('http://webservice......de/WFSService/WFSWebService?wsdl', $option); 
$headers = array('user' => 'guest', 'password' => 'guest'); 
$header = new SoapHeader('http://my_accessdomain_or_IP', 'AuthenticationDTO', $headers, false);  
$soapClient->__setSoapHeaders($header);
$params = array('pageSize'=>20, 'pageNumber' => 1, 'loadAllData'=> false);
try { 
    $result = $soapClient->__call("searchCompany", $params);
    print_r($result);
} catch (SoapFault $fault) { 
   echo $fault->faultcode . "-" . $fault->faultstring; 
   echo "REQUEST:\n" . htmlentities($soapClient->__getLastRequest()) . "\n";
}

?>

My Error request:
stdClass Object
(
[information] => stdClass Object
(
[informationType] => Error
[message] => The parameter UserInformation is null (modul AuthenticationManager).
[messageCode] => SystemExeption
[messageTemplate] => The parameter %s is null (modul %s).
[parameters] => Array
(
[0] => UserInformation
[1] => AuthenticationManager
)

[stackTrace] => stdClass Object