map list map list

map_to_list_to_map.php

<?php
declare(strict_types=1);

function mapToList(array $map): array
{
    $list = [];
    foreach ($map as $k => $v) {
        $list[] = \is_array($v)
            ? [$k, mapToList($v)]
            : [$k, $v];
    }
    return $list;
}

function listToMap(array $list): array
{
    return array_merge([], ...array_map(function (array $e): array {
        return [
            $e[0] => \is_array($e[1])
                ? listToMap($e[1])
                : $e[1],
        ];
    }, $list));
}

\assert(mapToList([]) === []);
\assert(listToMap([]) === []);
\assert(listToMap(mapToList([])) === []);
\assert(mapToList(listToMap([])) === []);
//
\assert(mapToList(['a' => 'b']) === [['a', 'b']]);
\assert(listToMap([['a', 'b']]) === ['a' => 'b']);
\assert(listToMap(mapToList(['a' => 'b'])) === ['a' => 'b']);
\assert(mapToList(listToMap([['a', 'b']])) === [['a', 'b']]);
//
\assert(mapToList(['a' => ['b' => ['c' => 'd']]]) === [['a', [['b', [['c', 'd']]]]]]);
\assert(listToMap([['a', [['b', [['c', 'd']]]]]]) === ['a' => ['b' => ['c' => 'd']]]);
\assert(listToMap(mapToList(['a' => ['b' => ['c' => 'd']]])) === ['a' => ['b' => ['c' => 'd']]]);
\assert(mapToList(listToMap([['a', [['b', [['c', 'd']]]]]])) === [['a', [['b', [['c', 'd']]]]]]);