Vmware Vcenter : AccountManager and virtualizationManager in Web Services are Unset

Hello everyone,

I'm actually trying to develop a PHP SOAP Client based on VMWare Vsphere Services SDK. I want to create and manager users in Vsphere through API. I can actually retrieve service content through web services, and get all ManagedObjetReferenced behind, except two of it : accountManager and virtualizationManager.

When i look into MOB, these are the only two which have as value "Unset", as you can see below.

Image may be NSFW.
Clik here to view.

Any idea on how I can set these values to retrieve them through Web Services ?

Regards

Jeremy