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

Question

I am trying to sum the values of two associative arrays. This is the first array:

Array
(
[Jan 01, 2013] => Array
    (
        [COM] => 100
        [         


        

Answer 1

Use foreach() for first array & check the key of first array whether it exist or not in second array. If exist the calculate sum. Example:

$arr1 = Array
(
    "Jan 01, 2013" => Array
    (
        "COM" => 100,
        "RES" => 200,
    ),

    "Oct 28, 2014" => Array
    (
        "COM" => 300,
        "RES" => 400,
    )
);
$arr2 = Array
(
    "Jan 01, 2013" => Array
    (
        "COM" => 10,
        "RES" => 20,
    ),

    "Oct 28, 2014" => Array
    (
        "COM" => 30,
        "RES" => 40,
   )
);

$arr3 = array();
foreach($arr1 as $key => $val):
    if(array_key_exists($key, $arr2)):
        $arr3[$key]["COM"] = $val["COM"] + $arr2[$key]["COM"];
        $arr3[$key]["RES"] = $val["RES"] + $arr2[$key]["RES"];
    endif;
endforeach;

print '<pre>';
print_r($arr3);
print '</pre>';

---

Output:

Array
(
    [Jan 01, 2013] => Array
        (
            [COM] => 110
            [RES] => 220
        )

    [Oct 28, 2014] => Array
        (
            [COM] => 330
            [RES] => 440
        )

)

Answer 2

Most directly/simply, iterate the levels of your second array and determine if the values should be appended to the first array, or merge-summed into it.

Code: (Demo)

$arr1 = [
    "Jan 01, 2013" => ["COM" => 100, "RES" => 200, "FOO" => 5],
    "Oct 28, 2014" => ["COM" => 300, "RES" => 400]
];
$arr2 = [
    "Jan 01, 2013" => ["COM" => 10, "RES" => 20],
    "Oct 28, 2014" => ["COM" => 30, "RES" => 40]
];

foreach ($arr2 as $date => $set) {
    foreach ($set as $key => $val) {
        if (!isset($arr1[$date][$key])) {            // val is unique to 1st array, set it
            $arr1[$date][$key] = $val;
        } else {                // val already exists in 1st array, add 2nd val to 1st val
            $arr1[$date][$key] += $val;
        }
    }
}
var_export($arr1);

---

Because you don't know the subarray keys for your incoming data and you have associative keys, you can use array_merge_recursive() to merge your two arrays in a way that sets up very simple summing.

After merging based on associative values, you can loop the new multi-dimensional array. While iterating, signify the subarray and the subarray's values as "modifiable by reference" -- this means that the foreach loops will process the actual array rather than a copy of the array. Effectively, this will make the changes affect the new array and deliver the desired result via $assoc_merged.

Code: (Demo)

$arr1 = [
    "Jan 01, 2013" => ["COM" => 100, "RES" => 200, "FOO" => 5],
    "Oct 28, 2014" => ["COM" => 300, "RES" => 400]
];
$arr2 = [
    "Jan 01, 2013" => ["COM" => 10, "RES" => 20],
    "Oct 28, 2014" => ["COM" => 30, "RES" => 40]
];

$assoc_merged =array_merge_recursive($arr1, $arr2);
// var_export($assoc_merged);  // see what this makes

foreach ($assoc_merged as $date => &$set) {
    foreach ($set as $key => &$val) {
        $val = array_sum((array)$val);
        // (array) forces a lone value to be an array containing one element; avoids generating Warnings
    }
}
var_export($assoc_merged);

---

Both approaches produce the same output:

array (
  'Jan 01, 2013' => 
  array (
    'COM' => 110,
    'RES' => 220,
    'FOO' => 5,
  ),
  'Oct 28, 2014' => 
  array (
    'COM' => 330,
    'RES' => 440,
  ),
)

Answer 3

Try this:

<?php
   $array_01 = array(
      'a' => 1,
      'b' => 2
   );

    $array_02 = array(
      'a' => 0,
      'b' => 1,
      'c' => 2
    );

    /** first we should get the array keys union
     * this is too long...,so you can make it better :D
     * you can make this more readable
     */
    $keyUnion = array_unique(array_merge(array_keys($array_01), array_keys($array_02))); 
    $res = array();

    //sum
    foreach ($keyUnion as $k => $v) {
        $res[$v] = (isset($array_01[$v]) ? $array_01[$v] : 0) + (isset($array_02[$v]) ? $array_02[$v] : 0);
    }

    print_r($res);
?>

Notice: code only get the one-dimensional associative sum