using array_map to get inner value of multi dimensional array

Array
(
    [0] => Array
    (
        [Detail] => Array
        (
            [detail_id] => 1
        )

    )

    [1] => Array
    (
        [Detail] => Array
        (
            [detail_id] => 4
        )

    )
)

If you want to get detail_id  to get 1,4.

$b = array_map(function($item) { return $item['Detail']['detail_id']; }, $test);

echo implode(",",$b);