乘以2个数组多维并删除键

Question

I have an multidimensional array which contain some numbers, and i want to multiplying value of array which contain key 0 with each other key inside one area array and erase key 0.

Array

Array
(
    [0] => Array
        (
            [0] => 3
            [1] => 5
            [2] => 5
            [3] => 6
            [4] => 7
        )

    [1] => Array
        (
            [0] => 2
            [1] => 7
            [2] => 4
            [3] => 2
            [4] => 8
        )

    [2] => Array
        (
            [0] => 4
            [1] => 2
            [2] => 3
            [3] => 2
            [4] => 5
        )
)

Here's the result i want

Array
(
    [0] => Array
        (
            [0] => 15
            [1] => 15
            [2] => 18
            [3] => 21
        )

    [1] => Array
        (
            [0] => 14
            [1] => 8
            [2] => 4
            [3] => 16
        )

    [2] => Array
        (
            [0] => 8
            [1] => 12
            [2] => 8
            [3] => 20
        )
)

I was already combine it using foreach and for, but it still not working for me, any idea how to do this?

Answer 1

The solution using array_map and array_slice functions:

// $arr is your initial array
foreach ($arr as &$v) {
    $multiplier = $v[0];
    $v = array_map(function($val) use($multiplier){
        return  $multiplier * $val;        
    }, array_slice($v, 1));
}

print_r($arr);

The output:

Array
(
    [0] => Array
        (
            [0] => 15
            [1] => 15
            [2] => 18
            [3] => 21
        )

    [1] => Array
        (
            [0] => 14
            [1] => 8
            [2] => 4
            [3] => 16
        )

    [2] => Array
        (
            [0] => 8
            [1] => 12
            [2] => 8
            [3] => 20
        )
)