Sort multi-dimensional array - keep values of keys

Question

I want to sort my array based on the key (which is a date) - preferrably both ASC and DESC.

I have tried to use several of the methods on SO, but keep getting bad results - so I thought I would ask the question again.

I have this array:

Array
(
    [2015-05-29] => Array
        (
            [a] => 13
            [b] => 1
            [c] => 12
        )

    [2015-05-28] => Array
        (
            [a] => 10
            [b] => 1
            [c] => 1
        )

    [2015-05-27] => Array
        (
            [a] => 2
        )

    [2015-05-30] => Array
        (
            [b] => 24
            [c] => 25
        )

)

I use this function - which should work according to several posts:

uasort($days, function($a, $b) {
    return $a['points'] - $b['points'];
}); 

But it doesn't, as the array gets returned like this:

    Array
    (
        [2015-05-30] => Array
            (
                [b] => 24
                [c] => 25
            )

        [2015-05-27] => Array
            (
                [a] => 2
            )

        [2015-05-28] => Array
            (
                [a] => 10
                [b] => 1
                [c] => 1
            )

        [2015-05-29] => Array
            (
                [a] => 13
                [b] => 1
                [c] => 12
            )

    )

I want to have the array returned like this:

   Array
(
    [2015-05-27] => Array
        (
            [a] => 2
        )

    [2015-05-28] => Array
        (
            [a] => 10
            [b] => 1
            [c] => 1
        )

    [2015-05-29] => Array
        (
            [a] => 13
            [b] => 1
            [c] => 12
        )

    [2015-05-30] => Array
        (
            [b] => 24
            [c] => 25
        )

)

or in reverse order!

Who can help me solve this problem?

Answer 1

You don't need any own sorting function. Just use ksort() / krsort() , .eg

//ASC         //DESC
ksort($arr);  //krsort($arr);