Combine 2 PHP arrays to create a leaderboard

Question

I have 2 arrays - Dealerships and Scores:

Dealerships

Array(
    [0] => Test Dealership 2
    [1] => Test Dealership
    [2] => Test Dealership
    [3] => Test Dealership 3
    [4] => Test Dealership
)

Scores

Array(
    [0] => 0
    [1] => 427
    [2] => 266
    [3] => 375
    [4] => 180
)

All I am trying to do is create a leaderboard that looks like this:

It needs to combine the scores for matching dealerships.

---

Dealership Leaderboard

1. Test Dealership - 873
2. Test Dealership 3 - 375
3. Test Dealership 2 - 0

---

I have mapped the arrays to create this:

Array
(
    [0] => Array
        (
            [0] => Test Dealership 2
            [1] => 0
        )

    [1] => Array
        (
            [0] => Test Dealership
            [1] => 427
        )

    [2] => Array
        (
            [0] => Test Dealership
            [1] => 266
        )

    [3] => Array
        (
            [0] => Test Dealership 3
            [1] => 375
        )

    [4] => Array
        (
            [0] => Test Dealership
            [1] => 180
        )

)

But I'm drawing a blank on how to get to the next stage.

Answer 1

You're probably looking for a function like this:

function reduce_total_scores($input) {
        $output = array_reduce($input, function ($carry, array $current) {
                if (!isset($carry[$current[0]])) $carry[$current[0]] = 0;
                $carry[$current[0]] += $current[1];
                return $carry;
        }, []);
        arsort($output);
        return $output;
}

To show it in action:

<?php

$dealerships = [
        'Test Dealership 2',
        'Test Dealership',
        'Test Dealership',
        'Test Dealership 3',
        'Test Dealership',
];

$scores = [
        0,
        427,
        266,
        375,
        180,
];

/**
 * Just a function to create the combined array as the poster did.
 */
function join_array_values(...$arrs) {
        $result = [];
        $l = array_reduce($arrs, function ($carry, array $current) {
                $l = sizeof($current);
                return ($carry >= $l) ? $carry : $l;
        }, 0);
        foreach ($arrs as $i => $arr) {
                $arr = array_values($arr); // only take values
                for ($j=0; $j<$l; $j++) {
                        $result[$j][$i] = $arr[$j] ?? null;
                }
        }
        return $result;
}

/**
 * Reduce the totals of different dealerships
 */
function reduce_total_scores($input) {
        $output = array_reduce($input, function ($carry, array $current) {
                if (!isset($carry[$current[0]])) $carry[$current[0]] = 0;
                $carry[$current[0]] += $current[1];
                return $carry;
        }, []);
        arsort($output);
        return $output;
}

$input = join_array_values($dealerships, $scores);

echo "input\n------\n";
print_r($input);

echo "\nresult\n------\n";
print_r(reduce_total_scores($input));

Run Result:

input
------
Array
(
    [0] => Array
        (
            [0] => Test Dealership 2
            [1] => 0
        )

    [1] => Array
        (
            [0] => Test Dealership
            [1] => 427
        )

    [2] => Array
        (
            [0] => Test Dealership
            [1] => 266
        )

    [3] => Array
        (
            [0] => Test Dealership 3
            [1] => 375
        )

    [4] => Array
        (
            [0] => Test Dealership
            [1] => 180
        )

)

output
------
Array
(
    [Test Dealership] => 873
    [Test Dealership 3] => 375
    [Test Dealership 2] => 0
)

Should be easy to fashion an output from the assoc array produced by reduce_total_scores().