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();
?>