php - 如何从3维数组中求和一个值

Question

I have data as below :

Array
(
    [1] => Array
        (
            [A] => Array
                (
                    [AA] => 3
                    [AB] => 5
                )

            [B] => Array
                (
                    [BA] => 2
                )

    [2] => Array
        (
            [C] => Array
                (
                    [CA] => 4
                )

            [D] => Array
                (
                    [DA] => 1
                    [DB] => 2
                )
        )

    [3] => Array
        (
            [E] => Array
                (
                    [EA] => 1
                    [EB] => 2
                    [EC] => 3
                )

            [F] => Array
                (
                    [FA] => 0
                    [FB] => 7
                    [FC] => 7
                )
)

I want to sum the value and this is my expectation :

Array(
    [1] => 10        
    [2] => 7
    [3] => 20
)

Here is my code that I used for summing the value :

$total[$country_id][$province_id][$city_id] = $amount;

$result = array();
foreach( $total as $key => $val ){
         $total[$key] = array_sum ( $val );
}

can someone explain what is wrong with my code or explain how foreach work? because the result of my code is 0 and actually I just studied around 1 week about foreach. Thanks

Answer 1

As you want to know more about foreach, here is a more verbose solution using it :

$total = 0;
$totalByCountry = [];

// iterate over each country
foreach ($arr as $countryId => $provinces) {

    $totalByCountry[$countryId] = 0;

    // iterate over each province
    foreach ($provinces as $provinceId => $cities) {

        // iterate over each city
        foreach ($cities as $cityId => $value) {
            $totalByCountry[$countryId] += $value;
            $total += $value;
        }
    }
}

Result of var_dump(totalByCountry) :

array (size=3)
    1 => int 10
    2 => int 7
    3 => int 20

Result of var_dump($total) :

int 37

-- edit --

In real world project, you better be less verbose and use php functions made for this kind of situation like array_walk_recursive(), as in Philipp Maurer and Firoz Ahmad answers.