如何使用两列中的值对子数组进行分组，然后对第三列的值求和？

Question

This is a section of my array:

[1] => Array
(
    [quantity] => 2
    [product_id] => 1
    [option_id] => 22
)

[2] => Array
(
    [quantity] => 2
    [product_id] => 2
    [option_id] => 22
)

[3] => Array
(
    [quantity] => 3
    [product_id] => 2
    [option_id] => 22
)

[4] => Array
(
    [quantity] => 1
    [product_id] => 2
    [option_id] => 25
)

I wish to group/merge the subarrays by product_id and option_id.

Upon merging subarrays, I would like to sum the quantity values.

In my sample data, both subarrays [2] and [3] have 'product_id'=>2 and 'option_id'=>22. They should be merged together into one subarray with a quantity value of 5.

This is my expected output:

[1] => Array
(
    [quantity] => 2
    [product_id] => 1
    [option_id] => 22
)

[2] => Array
(
    [quantity] => 5
    [product_id] => 2
    [option_id] => 22
)

[3] => Array
(
    [quantity] => 1
    [product_id] => 2
    [option_id] => 25
)

*My first level keys are not associated with their subarrays so they may be changed in the process. I do want the first level keys to be incremented from 1 not 0.

Answer 1

You only need to build compound temporary keys and then overwrite the keys.

By writing an initial element (null in this case) then deleting the element after the loop is finished, you ensure that the first key in the result array is 1.

To avoid the "messiness" of the repeated long-winded compound key, you can save the the dynamic key as a variable in the first line inside of the foreach loop, then reference that variable in the three respective locations in the condition block.

Code (Demo)

$array = [
    1 => ['quantity' => 2, 'product_id' => 1, 'option_id' => 22],
    2 => ['quantity' => 2, 'product_id' => 2, 'option_id' => 22],
    3 => ['quantity' => 3, 'product_id' => 2, 'option_id' => 22],
    4 => ['quantity' => 1, 'product_id' => 2, 'option_id' => 25]
];

$result = [null];  // create placeholding element
foreach($array as $subarray){
    $composite_key = $subarray['product_id'] . '_' . $subarray['option_id'];
    if(!isset($result[$composite_key])){
        $result[$composite_key] = $subarray;  // first occurrence
    }else{
        $result[$composite_key]['quantity'] += $subarray['quantity'];  // not first occurrence
    }
}
$result=array_values($result);  // change from assoc to indexed
unset($result[0]);  // remove first element to start numeric keys at 1
var_export($result);

Output:

array (
  1 => 
  array (
    'quantity' => 2,
    'product_id' => 1,
    'option_id' => 22,
  ),
  2 => 
  array (
    'quantity' => 5,
    'product_id' => 2,
    'option_id' => 22,
  ),
  3 => 
  array (
    'quantity' => 1,
    'product_id' => 2,
    'option_id' => 25,
  ),
)