Description:
------------
When dealing with an incorrectly formatted serialized array (such as from a source other than PHP like a javascript, or hand-coded), unserialize() does not check and convert array keys that are stored as strings but should be integers.

This makes it impossible to recover the value through any sort of type-casting.


Reproduce code:
---------------
$badly_serialized_array = 'a:1:{s:1:"0";s:1:"a";}';
$back_to_an_array = unserialize($badly_serialized_array);
echo $back_to_an_array[0];
echo $back_to_an_array['0'];
$v = (string)'0';
echo $back_to_an_array[$v];


Expected result:
----------------
a
a
a

Actual result:
--------------
nothing
nothing
nothing