Description:
------------
When a method is called outside any instance, I would expect $this not being defined, however, if the method is called from another object, it will point to the caller.
Is it intended ?

Reproduce code:
---------------
<?php
        class Plop {
                function coin(){
                        echo get_class($this);
                }
        }
        class Foo {
                function plop(){
                        Plop::coin();
                }
        }
        $foo =& new Foo();
        $foo->plop();
?>

Expected result:
----------------
Nothing

Actual result:
--------------
foo