Multiplying 2 array multidimensional and remove key - php

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
)
)