Sum parts of an array in php - php

Question

this is quite beyond me. Appreciate some help.
I have an array in php like so:
[0] => Array
(
[cust_id] => 1006
[no_of_subs] => 2
[dlv_id] => 1000
)
[1] => Array
(
[cust_id] => 1011
[no_of_subs] => 3
[dlv_id] => 1000
)
[2] => Array
(
[cust_id] => 1012
[no_of_subs] => 5
[dlv_id] => 1001
)
[3] => Array
(
[cust_id] => 1013
[no_of_subs] => 6
[dlv_id] => 1001
)
I don't need the cust_id field. I just need to group the dlv_id and the sum of no_of_subs for each matching dlv_id. The result should look like this:
[0] => Array
(
[dlv_id] => 1000
[no_of_subs] => 5
)
[1] => Array
(
[cust_id] => 1011
[no_of_subs] => 11
)
Thank you for any help.
I don't understand the downvotes for this question. Am i doing it all wrong? Downvoting without a reason is not helping.

Answer 1

The simplest, most efficient way to group and sum is to perform a single loop and assign temporary associative keys.
When a row is identified as a new dlv_id row, save the two desired elements, otherwise add the no_of_subs value to the pre-existing value.
Optionally, remove the temporary keys with array_values().
Code (Demo)
$array = [
["cust_id" => 1006, "no_of_subs" => 2, "dlv_id" => 1000],
["cust_id" => 1011, "no_of_subs" => 3, "dlv_id" => 1000],
["cust_id" => 1012, "no_of_subs" => 5, "dlv_id" => 1001],
["cust_id" => 1013, "no_of_subs" => 6, "dlv_id" => 1001]
];
foreach ($array as $row) {
if (!isset($result[$row["dlv_id"]])) {
$result[$row["dlv_id"]] = ["dlv_id" => $row["dlv_id"], "no_of_subs" => $row["no_of_subs"]];
} else {
$result[$row["dlv_id"]]["no_of_subs"] += $row["no_of_subs"];
}
}
var_export(array_values($result));
Output:
array (
0 =>
array (
'dlv_id' => 1000,
'no_of_subs' => 5,
),
1 =>
array (
'dlv_id' => 1001,
'no_of_subs' => 11,
),
)

Answer 2

Using array_column function, we can extract out dlv_id and no_of_subs separately in two different arrays, using cust_id as the key.
Now, simply loop over the array of dlv_id, and if matching key found, add the no_of_subs to it, else set the value (for the first time).
We use isset function to check if the key exists already or not.
Try the following:
// your input array is $input_array
// get all dlv_id maintaining the cust_id as index
$dlv_id = array_column($input_array, 'dlv_id', 'cust_id');
// get all no_of_subs maintaining the cust_id as index
$no_of_subs = array_column($input_array, 'no_of_subs', 'cust_id');
$output = array();
foreach ($dlv_id as $key => $value) {
if (isset($output[$value]['dlv_id'])) {
$output[$value]['dlv_id'] += $no_of_subs[$key];
} else {
$output[$value]['dlv_id'] += $no_of_subs[$key];
}
}