If you want your SOAP client to be able to save and then retrieve the object properties, you need to set the SOAP server to be persistent by setting session.auto_start=0, invoking session_start(), and SoapServer->setPersistence(SOAP_PERSISTENCE_SESSION) in the following manner:
<?php
  ini_set("soap.wsdl_cache_enabled", 0);
  ini_set("session.auto_start", 0);
  require_once('MyClass.php');
  session_start();
  $server = new SoapServer('service.wsdl');
  $server->setClass("MyClass");
  $server->setPersistence(SOAP_PERSISTENCE_SESSION);
  $server->handle();
?>