Description:
------------
An array key passed to unset() from a variable doesn't seem to be typecasted anymore.


Test script:
---------------
This doesn't work anymore in PHP 5.4:

<?php
// This fails.
$array = array(1 => 2);
$a = "1";
unset($array[$a]);
print_r($array);

// Those works.
$array = array(1 => 2);
$a = 1;
unset($array[$a]);
print_r($array);

$array = array(1 => 2);
unset($array[1]);
print_r($array);

$array = array(1 => 2);
$a = 1;
unset($array["1"]);
print_r($array);
?>

Expected result:
----------------
Array
(
)
Array
(
)
Array
(
)
Array
(
)


Actual result:
--------------
Array
(
    [1] => 2
)
Array
(
)
Array
(
)
Array
(
)