Description:
------------
There is a simple html form
<input type="text" name="inventory[2391649236][product_code]" />

when post it, the $_REQUEST will be as below:
Array
(
    [inventory] => Array
        (
            [-1903318060] => Array
                (
                    [product_code] => 
                )
        )
)

Why 2391649236 become -1903318060?

In my case, "2391649236" is just unique index. I got it with sprintf("%u", 
crc32($my_data));

Test script:
---------------
<form>
<input type="text" name="inventory[2391649236][product_code]" />
<input type="submit" />
</form>
<?php print_r($_REQUEST) ?>

Expected result:
----------------
Array
(
    [inventory] => Array
        (
            [2391649236] => Array
                (
                    [product_code] => 
                )
        )
)

Actual result:
--------------
Array
(
    [inventory] => Array
        (
            [-1903318060] => Array
                (
                    [product_code] => 
                )
        )
)