Description:
------------
array_slice seems to be resetting the current array position *before* processing the offset parameter.

This makes it impossible to directly use expressions that use the array position for the offset parameter.

It would be mildly useful and less surprising if the parameters were evaluated before altering the array.

Reproduce code:
---------------
$a = range(0, 9);
next($a);
next($a);

$b = array_slice($a, key($a));

print_r($b);

Expected result:
----------------
Array
(
    [0] => 2
    [1] => 3
    [2] => 4
    [3] => 5
    [4] => 6
    [5] => 7
    [6] => 8
    [7] => 9
)


Actual result:
--------------
Array
(
    [0] => 0
    [1] => 1
    [2] => 2
    [3] => 3
    [4] => 4
    [5] => 5
    [6] => 6
    [7] => 7
    [8] => 8
    [9] => 9
)