I know this is probably something fairly simple, but I have not seen it before. What is the difference between:
I see it again when the function is called:
$instance =& somefunc();
Specifically what does the ampersand do?
It's a good thing to know what passing by reference is and how to use it properly. You're bound to run into it sooner or later.
I would avoid using passing by reference as it may lead to unexpected results. Here's a good article on it: http://schlueters.de/blog/archives/141-References-and-foreach.html