php - 反向迭代数组数组并从当前子数组值中减去以下子数组值

Question

我有一个像这样的动态多维数组：

$myarray = array(
            array(
                0 => 0,
                1 => 70, 
                2 => 19,
                3 => 0
            ),
            array(
                0 => 0,
                1 => 24,
                2 => 14
            ),
            array(
                0 => 0,
                1 => 15,
                2 => 11,
                3 => 0
            ),
            array(
                0 => 0,
                1 => 15,
                2 => 27,
                3 => 0
            )
        );

我需要遍历子数组并覆盖每个子数组的当前值，以表示原始值与子数组键的后续值之间的差异。

这描述了每个子数组元素所需的算术（后面的值=是新的所需值）：

$myarray = array(
            array(
                0 => 0 - 0 = 0
                1 => 70 - 24 = 46
                2 => 19 - 30 = -11
                3 => 0 - 0 = 0
            ),
            array(
                0 => 0 - 0 = 0
                1 => 24 - 0 = 24
                2 => 14 -(-16) = 30
                3 => 0 - 0 = 0
            ),
            array(
                0 => 0 - 0 = 0
                1 => 15 - 15 = 0
                2 => 11 - 27 = -16
                3 => 0 - 0 = 0
            ),
            array(
                0 => 0,
                1 => 15,
                2 => 27,
                3 => 0
            )
        );

我试图做某事，但这不是我需要的，它包含错误：

$new_array = array();
foreach($myarray as $key => $values) {
    foreach($values as $k_key => $v_values) {
        $calc = $values[$k_key+1]-$v_values;
        array_push($new_array , $calc);
    }
}
var_dump($new_array);

Answer 1

1. 从倒数第二个子数组开始，然后循环到开始
2. 找出两个目标数组中较长的数组长度
3. 迭代并执行减法/声明
4. 在遇到新值时声明/覆盖它们

代码：（演示）

$myarray = [
    [0, 70, 19, 0],
    [0, 24, 14],        // note missing 4th element
    [0, 15, 11, 0],
    [0, 15, 27, 0]
];

for ($i = count($myarray) - 2; $i >= 0; --$i) {
    $max = max(count($myarray[$i]), count($myarray[$i+1]));
    for($k = 0; $k < $max; ++$k) {
        $myarray[$i][$k] = ($myarray[$i][$k] ?? 0) - ($myarray[$i+1][$k] ?? 0);
    }
}

var_export($myarray);