Description:
------------
Altering a subindex of a copy of an array alters the original array as well.  Similar to bug#27381.  Altering a root index does not exhibit this behaviour.

Reproduce code:
---------------
<?php

$arr = array(1,2,3);
$arr["foo"] = array(4,5,6);
$copy = $arr;

unset($copy["foo"][0]);
print_r($arr);

?>

Expected result:
----------------
Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [foo] => Array
        (
            [0] => 4
            [1] => 5
            [2] => 6
        )

)


Actual result:
--------------
Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [foo] => Array
        (
            [1] => 5
            [2] => 6
        )

)