$value before the json_decode call : [[12051,840,501,33],{"23602":22}]

$value after json_decode call (output via print_r):
Array
(
    [0] => Array
        (
            [0] => 12051
            [1] => 840
            [2] => 501
            [3] => 33
        )

    [1] => Array
        (
            [23602] => 22
        )

)

$value[1] output via print_r:
Array
(
    [23602] => 22
)