Как собрать новый массив из массивов в цикле по совпадению «ключ» — «значение»?

Question

[daylight6]

Есть массив

array(2) {
  ["Moscow"] =>
    [0] =>
        ["PRODUCT_ID"] => 10
        ["PRICE_USD"] => 300
        ["PRICE_RUB"] => 12000
    [1]=>
        ["PRODUCT_ID"] =>  10
        ["PRICE_EUR"] => 345
        ["PRICE_RUB"] => 12000
     [2]=>
        ["PRODUCT_ID"] =>  11
        ["PRICE_USD"] => 15
        ["PRICE_RUB"] => 1000
  ["Saint-Petersburg"] =>
    [0] =>
        ["PRODUCT_ID"] => 15
        ["PRICE_USD"] => 300
        ["PRICE_RUB"] => 10000
    [1]=>
        ["PRODUCT_ID"] =>  12
        ["PRICE_EUR"] => 345
        ["PRICE_RUB"] => 12000
     [2]=>
        ["PRODUCT_ID"] =>  15
        ["PRICE_EUR"] => 15
        ["PRICE_RUB"] => 10000
}

Надо собрать из него такой массив

array(2) {
  ["Moscow"] =>
    [0] =>
        ["PRODUCT_ID"] => 10
        ["PRICE_USD"] => 300
        ["PRICE_EUR"] => 345
     [1]=>
        ["PRODUCT_ID"] =>  11
        ["PRICE_USD"] => 15
  ["Saint-Petersburg"]=>
    [0] =>
        ["PRODUCT_ID"] => 15
        ["PRICE_USD"] => 300
        ["PRICE_EUR"] => 15
    [1]=>
        ["PRODUCT_ID"] =>  12
        ["PRICE_EUR"] => 345
}

То есть, необходимо объединить массивы, в которых совпадает PRODUCT_ID.

Comments

[Алан Гибизов]

Рекомендую привести свою попытку, пусть неудачную. Иначе это не вопрос, а задание, см.п.5.12 правил.

[Сергей Соколов]

а почему рубли исчезли?

[daylight6]

Сергей Соколов, Алан Гибизов, дополняю информацию по вопросу:

Изначально массив имеет вид

Array
(
    [0] => Array
        (
            [PRODUCT_ID] => 10
            [PRICE_USD] => 300
            [PRICE_RUB] => 12000
            [REGION] => Moscow
        )

    [1] => Array
        (
            [PRODUCT_ID] => 10
            [PRICE_EUR] => 345
            [PRICE_RUB] => 12000
            [REGION] => Moscow
        )

    [2] => Array
        (
            [PRODUCT_ID] => 11
            [PRICE_USD] => 15
            [PRICE_RUB] => 1000
            [REGION] => Moscow
        )

    [3] => Array
        (
            [PRODUCT_ID] => 15
            [PRICE_USD] => 300
            [PRICE_RUB] => 10000
            [REGION] => Saint-Petersburg
        )

    [4] => Array
        (
            [PRODUCT_ID] => 12
            [PRICE_EUR] => 345
            [PRICE_RUB] => 12000
            [REGION] => Saint-Petersburg
        )

    [5] => Array
        (
            [PRODUCT_ID] => 15
            [PRICE_EUR] => 15
            [PRICE_RUB] => 10000
            [REGION] => Saint-Petersburg
        )

)

Далее я пересобираю массив с товарами, отсортированными по городам:

$sortByRegion = [];

foreach($result as $item) {
    $sortByRegion[$item['REGION']][] = $item;
}

Получается вот такое:

Array
(
    [Moscow] => Array
        (
            [0] => Array
                (
                    [PRODUCT_ID] => 10
                    [PRICE_USD] => 300
                    [PRICE_RUB] => 12000
                    [REGION] => Moscow
                )

            [1] => Array
                (
                    [PRODUCT_ID] => 10
                    [PRICE_EUR] => 345
                    [PRICE_RUB] => 12000
                    [REGION] => Moscow
                )

            [2] => Array
                (
                    [PRODUCT_ID] => 11
                    [PRICE_USD] => 15
                    [PRICE_RUB] => 1000
                    [REGION] => Moscow
                )

        )

    [Saint-Petersburg] => Array
        (
            [0] => Array
                (
                    [PRODUCT_ID] => 15
                    [PRICE_USD] => 300
                    [PRICE_RUB] => 10000
                    [REGION] => Saint-Petersburg
                )

            [1] => Array
                (
                    [PRODUCT_ID] => 12
                    [PRICE_EUR] => 345
                    [PRICE_RUB] => 12000
                    [REGION] => Saint-Petersburg
                )

            [2] => Array
                (
                    [PRODUCT_ID] => 15
                    [PRICE_EUR] => 15
                    [PRICE_RUB] => 10000
                    [REGION] => Saint-Petersburg
                )

        )

)

Затем опять пересобираю массивы так, чтобы ключом был ID товара:

$products = [];
foreach($sortByRegion as $key => $regionItems) {
    foreach($regionItems as $item) {
        $products[$key][$item['PRODUCT_ID']][] = $item; 
    }
}

Получается:

Array
(
    [Moscow] => Array
        (
            [10] => Array
                (
                    [0] => Array
                        (
                            [PRODUCT_ID] => 10
                            [PRICE_USD] => 300
                            [PRICE_RUB] => 12000
                            [REGION] => Moscow
                        )

                    [1] => Array
                        (
                            [PRODUCT_ID] => 10
                            [PRICE_EUR] => 345
                            [PRICE_RUB] => 12000
                            [REGION] => Moscow
                        )

                )

            [11] => Array
                (
                    [0] => Array
                        (
                            [PRODUCT_ID] => 11
                            [PRICE_USD] => 15
                            [PRICE_RUB] => 1000
                            [REGION] => Moscow
                        )

                )

        )

    [Saint-Petersburg] => Array
        (
            [15] => Array
                (
                    [0] => Array
                        (
                            [PRODUCT_ID] => 15
                            [PRICE_USD] => 300
                            [PRICE_RUB] => 10000
                            [REGION] => Saint-Petersburg
                        )

                    [1] => Array
                        (
                            [PRODUCT_ID] => 15
                            [PRICE_EUR] => 15
                            [PRICE_RUB] => 10000
                            [REGION] => Saint-Petersburg
                        )

                )

            [12] => Array
                (
                    [0] => Array
                        (
                            [PRODUCT_ID] => 12
                            [PRICE_EUR] => 345
                            [PRICE_RUB] => 12000
                            [REGION] => Saint-Petersburg
                        )

                )

        )

)

B затем вот так вроде как получилось собрать итоговый массив:

$finalResult = [];
foreach($products as $key => $product) {
    foreach($product as $productID => $productData) {
        $finalResult[$key][$productID] = array_merge([], ...$productData);
    }
}

Array
(
    [Moscow] => Array
        (
            [10] => Array
                (
                    [PRODUCT_ID] => 10
                    [PRICE_USD] => 300
                    [PRICE_RUB] => 12000
                    [REGION] => Moscow
                    [PRICE_EUR] => 345
                )

            [11] => Array
                (
                    [PRODUCT_ID] => 11
                    [PRICE_USD] => 15
                    [PRICE_RUB] => 1000
                    [REGION] => Moscow
                )

        )

    [Saint-Petersburg] => Array
        (
            [15] => Array
                (
                    [PRODUCT_ID] => 15
                    [PRICE_USD] => 300
                    [PRICE_RUB] => 10000
                    [REGION] => Saint-Petersburg
                    [PRICE_EUR] => 15
                )

            [12] => Array
                (
                    [PRODUCT_ID] => 12
                    [PRICE_EUR] => 345
                    [PRICE_RUB] => 12000
                    [REGION] => Saint-Petersburg
                )

        )

)

Меня смущает это количество переборов. Насколько адекватен такой код?

Answer 1

[Сергей Соколов]

можно через промежуточную структуру,
где ключ город+product_id, а значения – массив с остальными полями.

Answer 2

[0xD34F]

$result = [];

foreach ($arr as $key => $val) {
  foreach ($val as $n) {
    $result[$key][$n['PRODUCT_ID']][] = $n;
  }
}

$result = array_map(fn($n) => array_map(fn($m) => array_merge(...$m), array_values($n)), $result);