How to Sum Columns of a Multi-Dimensional Array?

Question

I have array data like :

[
    'A1' => [1, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    'A2' => [1, 1, 0, 0, 0, 0, 0, 0, 0, 0],
    'A3' => [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
];

I want to add the column values and produce a flat array of sums.

I want answer like this:

[2, 1, 0, 0, 0, 0, 0, 0, 0, 0]

Are there any array functions in php to do this? Otherwise how can I do this?

Answer 1

There's always custom code:

function array_sum_rows($arr) {
    $out = array();
    foreach ($arr as $row) {
        foreach ($row as $i => $val) {
            $out[$i] = isset($out[$i]) ? $out[$i] + $val : $val;
        }
    }
    return $out;
}

Answer 2

$multiArray = ... //your array
$sumArray = array();
$i = 1;

foreach ($multiArray as $key => $array) {
    $sumArray[$i] = array_sum($array);
    $i++;
}

This would work with your array. You will get an array

http://php.net/manual/en/function.array-sum.php

Answer 3

Unfortunately loses the actual index in the transpose:

function array_transpose($arr) {
    return call_user_func_array(
        'array_map',
        array_merge(
            array(NULL),
            $arr
        )
    );
}

$transposedArray = array_transpose($myData);
$result = array_map('array_sum', $transposedArray);
var_dump($result);

But the indexes can be restored by

$result = array_combine(array_keys(end($myData)), $result);

Answer 4

"Transpose" the input array (rotate the data 90 degrees so that columns become rows), then feed the new "rows" to array_map() so that each has array_sum() called upon it.

Code: (Demo)

$array = [
    'A1' => [1, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    'A2' => [1, 1, 0, 0, 0, 0, 0, 0, 0, 0],
    'A3' => [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
];

var_export(array_map('array_sum', array_map(null, ...array_values($array))));

*Calling array_values() is necessary before the spread operator (...) until using a php version that doesn't choke on string keys.

Produces flat output array: [2, 1, 0, 0, 0, 0, 0, 0, 0, 0]