$client = new SoapClient($wsdlUrl);
$sendLastNewsletterRequest = new StdClass();
$sendLastNewsletterRequest->mandatorId = 0;
$sendLastNewsletterRequest->recipients = array();
$recipient = new StdClass();
$recipient->emailAddress = "user@example.com";
$recipient->newsletterListIds = array(1);
$recipient->subscriberFields = array();
$subscriberField = new StdClass();
$subscriberField->fieldName = utf8_encode ("VORNAME");
$subscriberField->fieldValue = utf8_encode ("Marcel");
array_push($recipient->subscriberFields, $subscriberField);
$subscriberField = new StdClass();
$subscriberField->fieldName = utf8_encode ("NACHNAME");
$subscriberField->fieldValue = utf8_encode ("Hartwig");
array_push($recipient->subscriberFields, $subscriberField);
array_push($sendLastNewsletterRequest->recipients, $recipient);
try {
  $result = $client->sendLastNewsletter($sendLastNewsletterRequest);
  var_dump($result);
} catch (Exception $e) {
  echo "Fehler aufgetreten: " . $e->getMessage() . "\r\n";
}