update_view_data() is probably the method you want.
$vm->update_view_data();
You could also get a bit more robust and leverage the WaitForUpdatesEx() method of the PropertyCollector. Then you could just have a list of entities (VMs, Hosts, etc) and have those updated on demand with just changes in a single API invocation. But usually the update_view_data() method works in most cases without the extra complexity.
Reuben Stump | http://www.virtuin.com | @ReubenStump