PHP：聚合数组[重复]

Question

This question already has an answer here:

• Sum the values of two associative multi-dimensional arrays in PHP 3 answers

Assuming I have the following 3 PHP arrays:

$arr1 = [1,2,3,4]
$arr2 = [5,2,4,1]
$arr3 = [2,1,2,2]

What's the most efficient built-in way that PHP has to add these arrays to elements in the same index of each array. Meaning, the final output would be the following:

$final = [8,5,9,7]

There should be an easier way than doing final = [$arr1[0]+$arr2[0]+$arr3[0]..] etc. Also, I need to assume there's a variable amount of arrays, so hard coding the math like above isn't correct.

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Answer 1

Make them all one array and use array_sum and array_column

$arr1 = [1,2,3,4];
$arr2 = [5,2,4,1];
$arr3 = [2,1,2,2];

$all = [$arr1, $arr2, $arr3];

foreach($all[0] as $key => $v){
    $result[$key] = array_sum(array_column($all, $key));
}

var_dump($result);

Output:

array(4) {
  [0]=>
  int(8)
  [1]=>
  int(5)
  [2]=>
  int(9)
  [3]=>
  int(7)
}

https://3v4l.org/qndQH

This method will only work if all arrays are same length or the first is the longest.

---

If you have an unknown amount of arrays within an name range then you can loop and use isset to see if the array exist, if yes add it to $all.

$arr1 = [1,2,3,4,5];
$arr2 = [5,2,4,1];
$arr3 = [2,1,2,2];
$arr4 = [2,1,2,2];
$all = [];

$i=1;
while(isset(${"arr" . $i})){
    $all[] = ${"arr" . $i};
    $i++;
}

foreach($all[0] as $key => $v){
    $result[$key] = array_sum(array_column($all, $key));
}

var_dump($result);

---

If you want it all super dynamic then you can use the code above and add what subarray is the longest and loop that in the last loop.

$arr1 = [1,2,3,4,5];
$arr2 = [5,2,4,1];
$arr3 = [2,1,2,2];
$arr4 = [2,1,2,2];
$arr5 = [2,1,2,2,6,1,3,2];
$all = [];

// Add all subarrays dynamically and see which is the longest
$i=1;
$count = Null;
while(isset(${"arr" . $i})){
    $all[] = ${"arr" . $i};
    if(count(${"arr" . $i}) > $count){
        $count = count(${"arr" . $i});
        $longkey = $i-1;
    }
    $i++;
}

// Loop the longest subarray
foreach($all[$longkey] as $key => $v){
    $result[$key] = array_sum(array_column($all, $key));
}

var_dump($result);

Working example:
https://3v4l.org/lIVGo