Recursively Merging Associative PHP Arrays

<?php
function array_merge_recursive_distinct(array ...$arrays): array {
    $merged = array_shift($arrays); // Start with the first array
    if (!is_array($merged)) {
        return $merged; // Not an array, return as is
    }

    foreach ($arrays as $array) {
        foreach ($array as $key => $value) {
            if (is_array($value) && isset($merged[$key]) && is_array($merged[$key])) {
                $merged[$key] = array_merge_recursive_distinct($merged[$key], $value);
            } else {
                $merged[$key] = $value;
            }
        }
    }
    return $merged;
}

$defaultConfig = [
    'database' => [
        'host' => 'localhost',
        'user' => 'root',
        'password' => '',
        'options' => ['charset' => 'utf8']
    ],
    'app' => [
        'name' => 'MyApp',
        'debug' => true
    ]
];

$userConfig = [
    'database' => [
        'user' => 'admin',
        'password' => 'newpass',
        'options' => ['port' => 3306] // New option
    ],
    'app' => [
        'debug' => false,
        'log_level' => 'info' // New setting
    ],
    'cache' => [ // Entirely new section
        'driver' => 'file'
    ]
];

$finalConfig = array_merge_recursive_distinct($defaultConfig, $userConfig);
print_r($finalConfig);

// Output:
// Array
// (
//     [database] => Array
//         (
//             [host] => localhost
//             [user] => admin
//             [password] => newpass
//             [options] => Array
//                 (
//                     [charset] => utf8
//                     [port] => 3306
//                 )
//         )
//
//     [app] => Array
//         (
//             [name] => MyApp
//             [debug] => 
//             [log_level] => info
//         )
//
//     [cache] => Array
//         (
//             [driver] => file
//         )
//
// )
?>