md arrays

I have an array that looks something like this: $cart => Array ( [0] => Array

                (
                    [id] => LT4697
                    [qty] => 1
                )

            [1] => Array
                (
                    [id] => LT4153
                    [qty] => 3
                )

            [2] => Array
                (
                    [id] => LT4697
                    [qty] => 1
                )

) I'm aware that I probably could just have a single dimension array, but there's more to be added later, and I prefer to treat this data like rows from mysql. Anyway, what's the *least expensive* way to: - check if an item (eg LT4153) is in the cart already? - get the current qty of an item (eg LT4153) The cart won't be big, so a foreach() on the cart isn't out of question, but I'd like to know the *right* way :) TIA Justin