PHP在多维数组中添加特定键

Question

Let's say I have Array A

Array
(
    [0] => Array
        (
            [0] => 1491292800000
            [1] => 30
        )

    [1] => Array
        (
            [0] => 1491296400000
            [1] => 20
        )
        ....

Also we have Array B

Array
(
    [0] => Array
        (
            [0] => 1491292800000
            [1] => 15
        )

    [1] => Array
        (
            [0] => 1491296400000
            [1] => 10
        )
        ....

How would we add the inner value of [1] together to create

Array
(
    [0] => Array
        (
            [0] => 1491292800000
            [1] => 45
        )

    [1] => Array
        (
            [0] => 1491296400000
            [1] => 30
        )
        ....

Both arrays will have the exact same number of elements, in the same order (as defined by the unix timestamp in [0])

Answer 1

The simplest solution would be to use array_map.

$a = [
    [1491292800000, 30],
    [1491296400000, 20],
];
$b = [
    [1491292800000, 15],
    [1491296400000, 10],
];

$merged = array_map(function ($a, $b) {
    $a[1] += $b[1];
    return $a;
}, $a, $b);