Calculations in a multidimensional array - php

Question

I have an array which contains sub-elements that have several occurrences of the same element with different quantity:
Example array:
Array
(
[7] => Array
(
[id] => 11399
[groupid] => 18
[name] => Morphite
[quantity] => 150
)
[8] => Array
(
[id] => 16673
[groupid] => 429
[name] => Fernite Carbide
[quantity] => 44
)
[9] => Array
(
[id] => 16678
[groupid] => 429
[name] => Sylramic Fibers
[quantity] => 11
)
[10] => Array
(
[id] => 16673
[groupid] => 429
[name] => Fernite Carbide
[quantity] => 17
)
[11] => Array
(
[id] => 16680
[groupid] => 429
[name] => Phenolic Composites
[quantity] => 6
)
[12] => Array
(
[id] => 33361
[groupid] => 429
[name] => Plasmonic Matamaterials
[quantity] => 2
)
[13] => Array
(
[id] => 16681
[groupid] => 429
[name] => Nanotransistors
[quantity] => 2
)
[14] => Array
(
[id] => 16673
[groupid] => 429
[name] => Fernite Carbide
[quantity] => 22
)
)
What I want to do, is add all the elements with the same name / id together so that I'll be able to display one line with the right quantity.

Answer 1

Pretty simple to do with a loop.
//create new array to hold new array format
$new_array = [];
//loop through old array
foreach($old_array as $value) {
//check if $value['id'] key exists in `$new_array`
if(!array_key_exists($value['id'], $new_array)) {
//if key does not exist, create it
$new_array[$value['id']] = $value;
} else {
//if key does already exist, increment quantity
$new_array[$value['id']]['quantity'] += $value['quantity'];
}
}
Output from your example array:
Array
(
[11399] => Array
(
[id] => 11399
[groupid] => 18
[name] => Morphite
[quantity] => 150
)
[16673] => Array
(
[id] => 16673
[groupid] => 429
[name] => Fernite Carbide
[quantity] => 83
)
[16678] => Array
(
[id] => 16678
[groupid] => 429
[name] => Sylramic Fibers
[quantity] => 11
)
[16680] => Array
(
[id] => 16680
[groupid] => 429
[name] => Phenolic Composites
[quantity] => 6
)
[33361] => Array
(
[id] => 33361
[groupid] => 429
[name] => Plasmonic Matamaterials
[quantity] => 2
)
[16681] => Array
(
[id] => 16681
[groupid] => 429
[name] => Nanotransistors
[quantity] => 2
)
)
If you want the keys in this output array to be sequential numbers for some reason, you can achieve that by using array_values($new_array) after the loop.