How to sort a multidimensional array in a multidimensional array in PHP

I'm not able to solve this problem. I tried mostly everything.

I'm doing a home project with a database of song artists and their songs but i stumbled over a big problem which i cannot solve. I read most stackoverflow posts but none helped. I bombarded google with questions about php sorting methods and tried them but without success.

I would really appreciate help. I'm stuck on this for 3 days now...

Here is my problem:

I have my array with my artists ($arr) now how can i sort every song array of each artist by year? The data comes from an .json file.

$arr = array(
    "artists" => array(
        "1" => array(
            "id" => "1",
            "firstname" => "John",
            "lastname" => "Doe",
            "songs" => array(
                array("name" => "song_1", "year" => "1999"),
                array("name" => "song_2", "year" => "1987")
            ),
        ),
        "2" => array(
            "id" => "2",
            "firstname" => "Jane",
            "lastname" => "Doe",
            "songs" => array(
                array("name" => "song_1", "year" => "2000"),
                array("name" => "song_2", "year" => "1999")
            )
        ),
        "3" => array(
            "id" => "3",
            "firstname" => "Mark",
            "lastname" => "Doe",
            "songs" => array(
                array("name" => "song_1", "year" => "1984"),
                array("name" => "song_2", "year" => "1983")
            )
        )
    )
);

I hope, my problem is clear enough. I'm new here and i'm not really friends yet with all the buttons. I just can't wait, to hopefully solve this...

Use array_walk() and usort(). array_walk() is to make an iteration over the array and usort() is to sorting the songs by ASC or DESC order.

array_walk($arr['artists'], function (&$song) {
    usort($song['songs'], function ($a, $b) { return $a['year'] > $b['year'] ? 1 : -1; }); // Ascending order
    //usort($song['songs'], function ($a, $b) { return $a['year'] < $b['year'] ? 1 : -1; }); // Descending order
});

Demo