Sum column values from multiple arrays

Question

I have an arrays with dynamic name. My array could be more than 3, depends and array variable should be unique

$loopThrice = 3;
$getSum = 0;
$total = array();

$array0 = array(5, 10, 15, 20, 25, 30);
$array1 = array(1, 2, 3, 4, 5, 6);
$array2 = array(2, 6, 8, 10, 12, 14);

for($a=0; $a < $loopThrice; $a++){ // loop 3x to get unique array name
    foreach (${'array'.$a} as $key => $value) { // $array0, $array1, $array2,  
        //Right here is my problem, I'm not sure if this the correct way to get the sum of $array0,1,2
        
        //get the sum of array0,1,2 -- newarray(8, 18, 26, 34, 42, 50)
        $getSum += 
            //store newarray
            array_push($total, $getSum);     
    }
}

I need to get an output like this:

Array ( 
    [0] => 8
    [1] => 18 
    [2] => 26 
    [3] => 34 
    [4] => 43 
    [5] => 50 
)

You probably want to take a look at: http://stackoverflow.com/q/797251/3933332 to transpose your array and then you can call `array_sum()` on each subArray with either a foreach loop or `array_map()` — Rizier123, Sep 14 '16 at 14:01
You should put your arrays in one multi-dimensional array, that would make this a lot easier and you would not be limited to a fixed number of sub-arrays. — jeroen, Sep 14 '16 at 14:02
@jeroen Thanks that is a big idea so far i can only do is one dimension i never knew it could be possible in multi dimension. so think my question is wrong — Echoing Throughout Tel Numara, Sep 14 '16 at 14:13

Kevin Kopf · Accepted Answer · 2016-09-14T14:51:23.293

Why aren't you using a multidimensional array?

$array = array(); // hungarian notation
$array[] = array(5, 10, 15, 20, 25, 30);
$array[] = array(1, 2, 3, 4, 5, 6);
$array[] = array(2, 6, 8, 10, 12, 14);

In this case you will have an array of arrays:

Array
(
[0] => Array
    (
        [0] => 5
        [1] => 10
        [2] => 15
        [3] => 20
        [4] => 25
        [5] => 30
    )

[1] => Array
    (
        [0] => 1
        [1] => 2
        [2] => 3
        [3] => 4
        [4] => 5
        [5] => 6
    )

[2] => Array
    (
        [0] => 2
        [1] => 6
        [2] => 8
        [3] => 10
        [4] => 12
        [5] => 14
    )
)

You can go with nested for loops:

$sumArray = array();
$arrayCount = count($array);
$elementCount = 0;

foreach($array as $subarray)
{
    $count = count($subarray);
    $elementCount = $elementCount < $count ? $count : $elementCount;
}

for($i = 0; $i < $elementCount; $i++)
{
    $sumArray[$i] = 0;

    for($j = 0; $j < $arrayCount; $j++)
    {
        $sumArray[$i] += $array[$j][$i];
    }
}

print_r($sumArray);

The output is

Array
(
    [0] => 8
    [1] => 18
    [2] => 26
    [3] => 34
    [4] => 42
    [5] => 50
)

Now, if you have a disproportioned sub-arrays (i.e. different count of elements in each sub-array), you will still get some sort of result, as missing elements will be assumed to be 0. So, with the input of:

$array = array(); // hungarian notation
$array[] = array(5, 10, 15, 20, 25);
$array[] = array(1, 2, 3, 4, 5, 6);
$array[] = array(2, 6, 8, 10);

You will still get the result:

Array
(
    [0] => 8
    [1] => 18
    [2] => 26
    [3] => 34
    [4] => 30
    [5] => 6
)

You can loop through the sub-arrays and get the max elements. Like I propose in my answer. Less restricting. — iliaz, Sep 14 '16 at 14:44
@iliaz I know, I was not sure whether to include another loop or not... — Kevin Kopf, Sep 14 '16 at 14:46
@Nordenheim, Thank you, iliaz answer also same output but i prefer this cuz i want to learn multi-dimension array. very clear and easy to understant — Echoing Throughout Tel Numara, Sep 14 '16 at 15:24

score 2 · Answer 2 · answered Sep 14 '16 at 14:29

Well the multi array is the way to go, but you can still do it this way:

 $loopThrice = 3;
 $getSum = 0;
 $total = array();

 $array0 = array(5, 10, 15, 20, 25, 30);
 $array1 = array(1, 2, 3, 4, 5, 6);
 $array2 = array(2, 6, 8, 10, 12, 14);
 // find which arrray has the most values
 for($a=0; $a < $loopThrice; $a++){
     $max_index = (count(${'array'.$a}) > $max_index ? count(${'array'.$a}) : $max_index);
 }

 for($i=0; $i < $max_index; $i++){
      for($a=0; $a < $loopThrice; $a++){
           $total[$i] += ${'array'.$a}[$i];
     }
 }

 print_r($total);
 // prints Array ( [0] => 8 [1] => 18 [2] => 26 [3] => 34 [4] => 42 [5] => 50 )

score 1 · Answer 3 · answered Sep 14 '16 at 14:20

This should work for you:

$array0 = array(5, 10, 15, 20, 25, 30);
$array1 = array(1, 2, 3, 4, 5, 6);
$array2 = array(2, 6, 8, 10, 12, 14);

$var_prefix = 'array';
$arr_count = 0;
$max_fields = 0;

while(isset(${$var_prefix.$arr_count})) {
    $data[] = ${$var_prefix.$arr_count};
    if(count(${$var_prefix.$arr_count})>$max_fields) {
        $max_fields = count(${$var_prefix.$arr_count});
    };

    $arr_count++;
}

for($i=0; $i<$max_fields; $i++) {
    $result[$i] = array_sum(array_column($data, $i));
}

echo '<pre>';
print_r($result);
echo '</pre>';
die();

mickmackusa · Answer 4 · 2022-04-22T06:09:01.517

I don't know why you have individual array variables, but the process remains the same as if you declare a single array containing those arrays as rows in a multi-dimensional array.

Once you have a multi-dimensional array, the spread operator (...) will feed columns of data into array_map()'s custom function body -- where array_sum() can be called upon.

This task is effectively summing transposed data.

Code: (Demo)

var_export(
    array_map(fn() => array_sum(func_get_args()), $array0, $array1, $array2)
);

Or:

var_export(
    array_map(fn(...$cols) => array_sum($cols), $array0, $array1, $array2)
);

Output (from either approach):

array (
  0 => 8,
  1 => 18,
  2 => 26,
  3 => 34,
  4 => 42,
  5 => 50,
)

Sum column values from multiple arrays

4 Answers4

Linked