Description:
------------
When trying to reassign an object inside a function, it is not acting as passed by reference.

Reproduce code:
---------------
<?php
class foo {
}

function change($obj) {
  $obj = null;
}

function change_ref(&$obj) {
  $obj = null;
}

$o = new foo;

change($o);
var_dump($o);

change_ref($o);
var_dump($o);

Expected result:
----------------
Both should yield the same result.

1st: NULL
2nd: NULL

Actual result:
--------------
Only change_ref is redefining the object.

1st: 
object(foo)#1 (0) {
}

2nd: NULL