Cartesian Grouping

cartesian_grouping.php

<?php

function inject($elem, $array)
{
    return array_map(function ($n) use ($elem) {
        return array_merge((array) $elem, (array) $n);
    }, $array);
}

function zip($array1, $array2)
{
    return array_reduce(
        $array1,
        function ($v, $n) use ($array2) {
            return array_merge($v, inject($n, $array2));
        },
        array()
    );
}

function cartesian_product($array)
{
    $keys = array_keys($array);
    $prod = array_shift($array);
    $prod = array_reduce($array, 'zip', $prod);
    return array_map(function ($n) use ($keys) {
        return array_combine($keys, $n);
    }, $prod);
}

function getPrice($loans, $credit)
{
  // some logic
  return 100;
}

$loans = ['mortgage', 'car'];
$credits = ['good', 'bad'];
$amount = ['1000', '2000'];
$random = ['yes', 'no'];

$all = [$loans, $credits, $amount, $random];

collect(cartesian_product($all))
    ->mapToGroups(function ($dict) {
        $group = array_shift($dict);
        $subKey = implode('-', $dict);
        return [
            $group => [
                $subKey => getPrice(...$dict)
            ]
        ];
    })
    ->map(function ($values) {
        return array_merge(...$values);
    })
    ->toArray();