Merge and sum multiple multidimensional associative arrays PHP - php

Question

I have an array
$data = array(
1 => array(1 => 11 ,2 => 21, 3 => 31),
2 => array(1 => 21 ,2 => 22),
3 => array(1 => 31 ,2 => 23, 3 => 32),
);
which I want to transform to
$data = array(
1 => array(1 => 11 ,2 => 21, 3 => 31, 'Total' => 63),
2 => array(1 => 21 ,2 => 22, 'Total' => 43),
3 => array(1 => 31 ,2 => 23, 3 => 32, 'Total' => 83),
'Total' => array(1 => 63,2 => 46,3 => 63, 'Total' => 172),
);
the keys 1,2,3 are dynamic these could be 1 to 10 and also for sub array. Can you help ?

Answer 1

Most of the answers in Stack Overflow that I could find are related to either sum the elements within an array or the sum of different keys within a multi-dimensional array, but I couldn't find any that addressed both in the same code, so I thought it might be useful to share.
Premises
Your desired result seems incorrect, by manually doing the calculations the totals should be different than what you described. So I am assuming you just got your example wrong and this is the actual result you want:
$data = array(
1 => array(1 => 11 ,2 => 21, 3 => 31, 'Total' => 63),
2 => array(1 => 21 ,2 => 22, 'Total' => 43),
3 => array(1 => 31 ,2 => 23, 3 => 32, 'Total' => 86),
'Total' => array(1 => 63,2 => 66,3 => 63, 'Total' => 192),
);
Loop and sum arrays
So you basically want two things:
For each of the first-level elements of your arrays, you want to calculate the Total. This is done with array_sum and you can apply it by doing a foreach on the first level of your $data array. More info on array_sum and the official php documentation.
Then for each of the second-level elements, you want to sum the ones with the same key. To do so, you can use a simple foreach that keeps track of the second-level key and sums each value
Resulting Code
The resulting code combines these two points with the following logic:
Initialize the Totals key in the first-level of your $data array
Loop the first-level elements
For each first-level element, use array_sum to get the Total
Loop the second-level elements
For each Index of the second level (1, 2, 3), initialize the same index in the Totals array
For each Index of the second level (1, 2, 3), sum the counter (11, 21, 31) in the Totals array
I've added comments to make it clearer:
// Initialize the 'Total' key in the first-level of the array. This will be populated in the foreach
$data['Total'] = [];
// Loop the first level of the array
foreach ($data as $key => $values) {
// Calculate the sum of the first level of the array, using array_sum
$data[$key]['Total'] = array_sum($data[$key]);
// Loop the second level of the array
foreach ($values as $index => $count) {
// For each INDEX, create the corresponding element of the Totals array
if (!isset($data['Total'][$index])) {
$data['Total'][$index] = 0;
}
// Sum this element $count in the Total array
$data['Total'][$index] += $count;
}
}