Description:
------------
$this should not be defined in the context of a static function call.

Reproduce code:
---------------
class A {
    function func() {
        echo get_class($this);
    }
}

class B {
    function x() {
        A::func();
    }
}

$b = new B();
$b->x();


Expected result:
----------------
.. nothing .. (object not present/instantiated/defined)

Actual result:
--------------
b