Aggregate values in multidimensional array PHP - php

Question

From start I have a list of orders in the following way:
(
[product_id] => 1094
[total_weight] => 0.0390
[qty_ordered] => 10.0000
[category_id] => 12
)
What I want is to sum the values for total_weight and qty_ordered based on category_id
I have managed to get the array in the below manner now using a foreach. But I need to aggregate the values somehow.
Array
(
[14] => Array
(
[0] => Array
(
[product_id] => 1099
[total_weight] => 0.0390
[qty_ordered] => 10.0000
)
[1] => Array
(
[product_id] => 1095
[total_weight] => 0.0395
[qty_ordered] => 10.0000
)
)
[12] => Array
(
[0] => Array
(
[product_id] => 1094
[total_weight] => 0.0390
[qty_ordered] => 10.0000
)
)
[15] => Array
(
[0] => Array
(
[product_id] => 742
[total_weight] => 0.1250
[qty_ordered] => 1.0000
)
)
)
So ideally I would the output to be like with below with as little code as possible:
Array
(
[14] => Array
(
[total_weight] => 0.0785
[qty_ordered] => 20.0000
)
[12] => Array
(
[total_weight] => 0.0390
[qty_ordered] => 10.0000
)
[15] => Array
(
[total_weight] => 0.1250
[qty_ordered] => 1.0000
)
)

Answer 1

I was able to sort it in the below way.
foreach($retval as $val) {
$return[$val['category_id']]['qty_ordered'] += $val['qty_ordered'];
$return[$val['category_id']]['row_total'] += $val['row_total'];
}