Description:
------------
Seems, that multidimensional arrays are copied with one dimension, which contains references to other included arrays.

I haven't found any references in manual, so this must be a bug. 

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

$a[0]['id']    = array(22, 12, 33, 55);
$a[0]['secid'] = array("a","b","c","d");

print_r($a);

$b = $a;

foreach ($b as $k => $v) {
    array_multisort($v['id'], SORT_DESC, $v['secid'], SORT_DESC);
}

print_r($a);
?>

Expected result:
----------------
Array
(
    [0] => Array
        (
            [id] => Array
                (
                    [0] => 22
                    [1] => 12
                    [2] => 33
                    [3] => 55
                )

            [secid] => Array
                (
                    [0] => a
                    [1] => b
                    [2] => c
                    [3] => d
                )
        )
)
Array
(
    [0] => Array
        (
            [id] => Array
                (
                    [0] => 22
                    [1] => 12
                    [2] => 33
                    [3] => 55
                )

            [secid] => Array
                (
                    [0] => a
                    [1] => b
                    [2] => c
                    [3] => d
                )
        )
)


Actual result:
--------------
Array
(
    [0] => Array
        (
            [id] => Array
                (
                    [0] => 22
                    [1] => 12
                    [2] => 33
                    [3] => 55
                )

            [secid] => Array
                (
                    [0] => a
                    [1] => b
                    [2] => c
                    [3] => d
                )
        )
)
Array
(
    [0] => Array
        (
            [id] => Array
                (
                    [0] => 55
                    [1] => 33
                    [2] => 22
                    [3] => 12
                )

            [secid] => Array
                (
                    [0] => d
                    [1] => c
                    [2] => a
                    [3] => b
                )
        )
)