Sorry if this is a silly and/or stupid question but... Will there ever be, or would it even be possible to have a PHP.NET? Or have I got the wrong end of the stick?
Sure, there's a possibility. Python runs in the CLR, after all.
Side note: PHP is now a one-click install for IIS, so if you're waiting to bring PHP into your Microsoft stack, go ahead and give it a try. MS is even working on a PHP bytecode cache for Windows.