PHP在多维数组中添加特定键

假设我有数组A

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

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

我们还有数组B

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

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

我们如何将[1]的内部值相加以创建

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

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

---

两个数组的元素数量完全相同，顺序相同（由[0]中的unix时间戳定义）。

最简单的解决方案是使用

array\u 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);