Merge multi-dimensional arrays by relating first columns and summing two other columns

Question

I want to combine two multidimensional arrays in PHP.

print_r($array_a):

Array
(
[0] => Array
    (
        [0] => A
        [1] => 0
        [2] => 1047
    )

[1] => Array
    (
        [0] => B
        [1] => 0
        [2] => 279
    )

[2] => Array
    (
        [0] => C
        [1] => 0
        [2] => 68
    )

[3] => Array
    (
        [0] => D
        [1] => 0
        [2] => 4
    )

)

print_r($array_b):

Array
(
[0] => Array
    (
        [0] => A
        [1] => 76
        [2] => 0
    )

[1] => Array
    (
        [0] => B
        [1] => 170
        [2] => 0
    )

[2] => Array
    (
        [0] => C
        [1] => 15
        [2] => 0
    )

[3] => Array
    (
        [0] => D
        [1] => 210
        [2] => 0
    )
[4] => Array
    (
        [0] => E
        [1] => 287
        [2] => 0
    )

)

Then merge it, the result should be like this:

Array
(
[0] => Array
    (
        [0] => A
        [1] => 76
        [2] => 1047
    )

[1] => Array
    (
        [0] => B
        [1] => 170
        [2] => 279
    )

[2] => Array
    (
        [0] => C
        [1] => 15
        [2] => 68
    )

[3] => Array
    (
        [0] => D
        [1] => 210
        [2] => 4
    )
[4] => Array
    (
        [0] => E
        [1] => 287
        [2] => 0
    )

)

So the logic key is to merge the two array based on the first value of each array(A, B, C, D). And if there's an array that belong only in one of the array (for example, "E" on the array_b), I just add them. I tried this:

foreach($array_a as $a=>$array_now){
        foreach($array_b as $b=>$array_before){
            if($array_now[0] == $array_before[0]){
                $array_a[$a] = [$array_before[0], $array_before[1], $array_now[2]];
            }
        }
    }

But I can't seem to add the missing array (the 5th array in $array_b which contain 'E').

Possible duplicate of [PHP: Merge 2 Multidimensional Arrays](http://stackoverflow.com/questions/1558291/php-merge-2-multidimensional-arrays) — Masivuye Cokile, Nov 25 '16 at 10:34
@RJParikh I've updated the question according to your suggestion — IkouKuhn, Nov 25 '16 at 10:53

score 1 · Answer 1 · answered Nov 25 '16 at 11:16

use below code that will help you

$array_a = [];
$array_a[0][0] = 'A';
$array_a[0][1] = 0;
$array_a[0][2] = 1047;

$array_a[1][0] = 'B';
$array_a[1][1] = 0;
$array_a[1][2] = 279;

$array_a[2][0] = 'C';
$array_a[2][1] = 0;
$array_a[2][2] = 68;

$array_a[3][0] = 'D';
$array_a[3][1] = 0;
$array_a[3][2] = 4;


$array_b = [];
$array_b[0][0] = 'A';
$array_b[0][1] = 76;
$array_b[0][2] = 0;

$array_b[1][0] = 'B';
$array_b[1][1] = 70;
$array_b[1][2] = 0;

$array_b[2][0] = 'C';
$array_b[2][1] = 15;
$array_b[2][2] = 0;

$array_b[3][0] = 'D';
$array_b[3][1] = 210;
$array_b[3][2] = 0;

$array_b[3][0] = 'E';
$array_b[3][1] = 287;
$array_b[3][2] = 0;

$array_b[4][0] = 'E';
$array_b[4][1] = 2870;
$array_b[4][2] = 0;


$cnt = 0;
if(count($array_b) > $array_a){
    $cnt =  count($array_b);
}else{
    $cnt =  count($array_a);
}


$array_new = [];
for($i=0; $i <= $cnt; $i++){
    $array_new[$i] = [];

    if(isset($array_a[$i][0])){
        $array_new[$i][0] = $array_a[$i][0];
    }else{
        $array_new[$i][0] = $array_b[$i][0];    
    }   

    if(isset($array_b[$i][1])){
        $array_new[$i][1] = $array_b[$i][1];
    }else{
        $array_new[$i][1] = 0;  
    }

    if(isset($array_a[$i][2])){
        $array_new[$i][2] = $array_a[$i][2];
    }else{
        $array_new[$i][2] = 0;  
    }


}

echo "<pre>";
print_r($array_new);

Hope this will help!

score 0 · Answer 2 · answered Nov 25 '16 at 11:09

You could use multiple array_maps to achieve this

$c = array_map(function() {
    return array_map(function() {
        foreach (func_get_args() as $arg) {
            if ($arg) return $arg;
        }
        return func_get_arg(0);
    }, ...func_get_args());
}, $a, $b);

this code would also work with more than $a, $b - just add as much arrays as you want as param

IkouKuhn · Answer 3 · 2016-11-25T13:11:41.050

Sorry but all the above solution doesn't work, and I figured it by myself, by using this code:

    $result = array();
    if (count($array_a) > count($array_b)){
        foreach($array_a as $a=>$array_now){
            foreach($array_b as $b=>$array_before){
                if($array_now[0] == $array_before[0]){
                    $array_a[$a] = [(string)$array_before[0], (int)$array_before[1], (int)$array_now[2]];
                }
            }
        }
        $result = $array_a;
    } else {
        foreach($array_b as $a=>$array_now){
            foreach($array_a as $b=>$array_before){
                if($array_now[0] == $array_before[0]){
                    $array_b[$a] = [(string)$array_before[0], (int)$array_now[1], (int)$array_before[2]];
                }
            }
        }
        $result = $array_b;
    }

Thank you guys for all of your response.

score 0 · Answer 4 · answered Jan 17 '21 at 12:33

This task can be concisely, efficiently, and reliably performed with a single loop which generates a result array with temporary key to determine whether a new row is encountered or not.

Code: (Demo)

$array_a = [
  ['A', 0, 1047],
  ['B', 0, 279],
  ['C', 0, 68],
  ['D', 0, 4],
];

$array_b = [
  ['A', 76, 0],
  ['B', 170, 0],
  ['E', 287, 0],
  ['C', 15, 0],
  ['D', 210, 0],
];


foreach (array_merge($array_a, $array_b) as $row) {
    if (!isset($result[$row[0]])) {
        $result[$row[0]] = $row;
    } else {
        $result[$row[0]][1] += $row[1];
        $result[$row[0]][2] += $row[2];
    }
}
var_export(array_values($result));

Output:

array (
  0 => 
  array (
    0 => 'A',
    1 => 76,
    2 => 1047,
  ),
  1 => 
  array (
    0 => 'B',
    1 => 170,
    2 => 279,
  ),
  2 => 
  array (
    0 => 'C',
    1 => 15,
    2 => 68,
  ),
  3 => 
  array (
    0 => 'D',
    1 => 210,
    2 => 4,
  ),
  4 => 
  array (
    0 => 'E',
    1 => 287,
    2 => 0,
  ),
)

Merge multi-dimensional arrays by relating first columns and summing two other columns

4 Answers4