Custom Sorting Associative Arrays by Key

/**
 * Sorts an array of associative arrays by a given key (or multiple keys).
 * @param array $array The array to sort.
 * @param string|array $key The key(s) to sort by. Can be a string or an array of strings.
 * @param int $order The sort order (SORT_ASC or SORT_DESC). Applies to all keys if multiple.
 * @return array The sorted array.
 */
function sortAssociativeArrayByKey(array $array, string|array $key, int $order = SORT_ASC): array {
    if (empty($array)) {
        return [];
    }

    // Convert single key to an array for uniform processing
    $keys = is_string($key) ? [$key] : $key;

    usort($array, function($a, $b) use ($keys, $order) {
        foreach ($keys as $k) {
            $valA = $a[$k] ?? null; // Use null coalescing for safety
            $valB = $b[$k] ?? null;

            if ($valA === $valB) {
                continue; // Values are equal, move to next key
            }

            // Handle numeric vs. string comparison
            if (is_numeric($valA) && is_numeric($valB)) {
                $cmp = $valA <=> $valB;
            } else {
                $cmp = strcasecmp((string)$valA, (string)$valB);
            }

            return ($order === SORT_ASC) ? $cmp : -$cmp;
        }
        return 0; // All keys were equal
    });

    return $array;
}

$users = [
    ['id' => 1, 'name' => 'Alice', 'age' => 30],
    ['id' => 2, 'name' => 'Bob', 'age' => 25],
    ['id' => 3, 'name' => 'Charlie', 'age' => 35],
    ['id' => 4, 'name' => 'Aaron', 'age' => 25],
];

$sortedByName = sortAssociativeArrayByKey($users, 'name', SORT_ASC);
// $sortedByName will be sorted by name: Aaron, Alice, Bob, Charlie

$sortedByAgeThenName = sortAssociativeArrayByKey($users, ['age', 'name'], SORT_ASC);
// $sortedByAgeThenName will be sorted by age (25, 25, 30, 35) then by name for equal ages (Aaron, Bob)