Recursively Find Differences Between Two Associative Arrays

<?php
function array_diff_recursive(array $array1, array $array2): array {
    $diff = [];
    foreach ($array1 as $key => $value) {
        if (!array_key_exists($key, $array2)) {
            $diff[$key] = $value; // Key exists in array1 but not in array2
        } elseif (is_array($value) && is_array($array2[$key])) {
            $subDiff = array_diff_recursive($value, $array2[$key]);
            if (!empty($subDiff)) {
                $diff[$key] = $subDiff; // Recursive difference
            }
        } elseif ($value !== $array2[$key]) {
            $diff[$key] = $value; // Value is different
        }
    }
    return $diff;
}

$oldSettings = [
    'general' => [
        'name' => 'Old App',
        'version' => '1.0',
        'enabled' => true,
        'features' => ['A', 'B']
    ],
    'database' => [
        'host' => 'localhost',
        'port' => 3306
    ]
];

$newSettings = [
    'general' => [
        'name' => 'New App', // Changed
        'version' => '1.0',
        'features' => ['A', 'C'] // Changed, 'B' removed, 'C' added
    ],
    'database' => [
        'host' => '127.0.0.1' // Changed
    ],
    'logging' => [ // New section
        'level' => 'info'
    ]
];

// Find what's in $oldSettings that's different or missing in $newSettings
$changesFromOldToNew = array_diff_recursive($oldSettings, $newSettings);

// Expected Output:
// Array
// (
//     [general] => Array
//         (
//             [name] => Old App
//             [features] => Array
//                 (
//                     [0] => A
//                     [1] => B
//                 )
//         )
//     [database] => Array
//         (
//             [host] => localhost
//         )
// )
print_r($changesFromOldToNew);
// Note: This specific `array_diff_recursive` only shows elements that are in $array1
// but not in $array2, or are different. To show additions in $array2, you'd
// need to run it in reverse or combine with a check for new keys.
?>