How can I update a specific value in this array? (php)

Question

I have the following array, $cart which is structured like so:

Array
(
    [0] => Array
        (
            [sku] => TEST1
            [size] => s
            [qty] => 1
        )

)

how can I update the qty to 2 directly using php and not using a foreach loop (nb. assume I have the index value (0) already).

Thanks

Answer 1

Like this:

$array[0]['qty'] = 2;

Answer 2

Unless I'm missing something here, if you already know you want to update index 0:

$foo[0]['qty'] = 2;