Group rows of data and in each group sum one column and concatenate another column

Question

In php, I have an indexed array of associative rows like this:

$the_array = [
   ['id' => 1, 'value' => 10, 'name' => 'apple'],
   ['id' => 1, 'value' => 20, 'name' => 'orange'],
   ['id' => 1, 'value' => 30, 'name' => 'banana'],
   ['id' => 2, 'value' => 100, 'name' => 'car'], 
   ['id' => 2, 'value' => 200, 'name' => 'bicycle'],
];

and I would like to restructure it to by grouping on id values and in each group I'd like to sum the value values and make a comma-separated string of the name values.

[
    ['id' => 1, 'value' => 60,  'name' => 'apple,orange,banana'],
    ['id' => 2, 'value' => 300, 'name' => 'car,bicycle']
]

This is what I tried:

function group_by($key, $data) {
    $result = array();
    foreach($data as $val) {
        if(array_key_exists($key, $val)){
            $result[$val[$key]][] = $val;
        }else{
            $result[""][] = $val;
        }
    }
    return $result;
}

It's not working and the result is wrong/incomplete.

Answer 1

I would create an intermediary array which groups into array keys by id first, then use that to call combinations of array_column() with array_sum() and implode() to produce your sum value and combined name string.

$temp_array = [];
foreach ($the_array as $init) {
  // Initially, group them on the id key as sub-arrays
  $temp_array[$init['id']][] = $init;
}

$result = [];
foreach ($temp_array as $id => $arr) {
  // Loop once for each id ($temp_array has 2 elements from your sample)
  // And add an element to $result
  $result[] = [
    'id' => $id,
    // Sum the value subkeys
    // array_column() returns just the key 'value' as an array
    // array_sum() adds them
    'value' => array_sum(array_column($arr, 'value')),
    // implode the name subkeys into a string
    'name' => implode(',', array_column($arr, 'name'))
  ];
}

print_r($result);
Array
(
    [0] => Array
        (
            [id] => 1
            [value] => 60
            [name] => apple,orange,banana
        )

    [1] => Array
        (
            [id] => 2
            [value] => 300
            [name] => car,bicycle
        )

)