Can you have nested classes in PHP?

I'm not talking about inheritance. And I'm not talking about nested objects. I'm talking:

System::Web::Templating(...)

kind of nesting. These are classes of which you shouldn't create instances.. so...

No.

However, you could do something like this by returning an instantiated object in getInstance():

myClass::getInstance()->foo();

nope, you can’t nest classes in php. see: http://bytes.com/topic/php/answers/10138-nested-classes-php

It seems that you're speaking about namespaces, not about any kind of nesting. This feature was implemented in PHP 5.3, and is documented here.