Merge indexed array of associative arrays and sum the values of recurring keys

Question

I have a multidimensional array that looks like this:

Array
(
    [0] => Array
    (
        [GB] => 20827
        [US] => 73
        [ES] => 23
        [AU] => 15
        [DE] => 12
        [MY] => 4
        [QA] => 1
        [VN] => 1
        [SK] => 1
        [FJ] => 1
        [ME] => 1
        [TR] => 1
        [LV] => 1
    )

    [1] => Array
    (
        [GB] => 15070
        [US] => 3920
        [IE] => 1711
        [PH] => 1071
        [MT] => 578
        [AU] => 423
        [HR] => 241
        [ZA] => 210
        [FR] => 139
    )
)

I want to create a new array with all of the associative elements in each array of the multidimensional array and sum the values of duplicated keys.

Desired result from sample input:

array (
  'GB' => 35897,
  'US' => 3993,
  'ES' => 23,
  'AU' => 438,
  'DE' => 12,
  'MY' => 4,
  'QA' => 1,
  'VN' => 1,
  'SK' => 1,
  'FJ' => 1,
  'ME' => 1,
  'TR' => 1,
  'LV' => 1,
  'IE' => 1711,
  'PH' => 1071,
  'MT' => 578,
  'HR' => 241,
  'ZA' => 210,
  'FR' => 139,
)

score 1 · Accepted Answer · answered Mar 12 '16 at 01:01

Look through each of the sub-arrays, and then loop through the key/value pairs. Add them up in a $final array:

$final = [];
foreach($masterArray as $subArray) {
    foreach($subArray AS $key => $value) {
        $final[$key] = isset($final[$key])
            ? $final[$key] + $value
            : $value;
    }
}

Working example: https://3v4l.org/6XBbD

Tyler Sebastian · Answer 2 · 2016-03-12T01:00:04.523

0

perhaps something like

$array = count($array1) > count($array2) ? $array1 : $array2;
$otherArray = count($array1) > count($array2) ? $array2 : $array1;

array_walk($array, function(&$value, $key, $otherArray) {
    $value = $value + (isset($otherArray[$key]) ? $otherArray[$key] : 0);
}, $otherArray);

edited Mar 12 '16 at 01:00

answered Mar 12 '16 at 00:56

Tyler Sebastian

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The multidimensional array can be filled with more than 2 other arrays of data. Im trying to merge them all into one. – jackthedev Mar 12 '16 at 00:59
then process them one by one using the method above. – Tyler Sebastian Mar 12 '16 at 01:00

mickmackusa · Answer 3 · 2021-07-21T12:39:39.023

You can fast track this task by "shifting" the first row of data off of the input array and pushing the associative elements directly into the output array. This removes the need to execute any conditional operations on the first row which will improve efficiency.

Code: (Demo)

$result = array_shift($array);
foreach ($array as $row) {
    foreach ($row as $key => $value) {
        $result[$key] = ($result[$key] ?? 0) + $value;
    }
}
var_export($result);

Alterative with array_reduce(): (Demo)

$result = array_shift($array);
var_export(
    array_reduce(
        $array,
        function($result, $row) {
            foreach ($row as $key => $value) {
                $result[$key] = ($result[$key] ?? 0) + $value;
            }
            return $result;
        },
        $result
    )
);

Alternative with array_merge_recursive(): (Demo)

$result = array_shift($array);
array_walk_recursive(
    $array,
    function($value, $key) use(&$result) {
        $result[$key] = ($result[$key] ?? 0) + $value;
    }
);
var_export($result);

As a side effect of using array_shift(), if the input array is empty, then the output of all snippets above will be null instead of an empty array. If this is a deal-breaker for your project, then replace array_shift() with an empty array -- Demo.

Merge indexed array of associative arrays and sum the values of recurring keys

3 Answers3

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