/**
 * Recursively merges two associative arrays. Unlike array_merge_recursive, this function
 * overwrites existing scalar values and merges sub-arrays, rather than appending numeric keys.
 *
 * @param array $array1 The base array.
 * @param array $array2 The array to merge into the base array.
 * @return array The merged array.
 */
function array_merge_recursive_distinct(array $array1, array $array2): array
{
    $merged = $array1;

    foreach ($array2 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;
}

$config1 = [
    'database' => [
        'host' => 'localhost',
        'port' => 3306,
        'user' => 'root'
    ],
    'settings' => [
        'debug' => true,
        'locale' => 'en'
    ],
    'features' => ['A', 'B']
];

$config2 = [
    'database' => [
        'port' => 5432, // Overwrites port
        'password' => 'secret'
    ],
    'settings' => [
        'locale' => 'es', // Overwrites locale
        'timezone' => 'UTC'
    ],
    'new_feature' => true,
    'features' => ['C'] // Overwrites 'features' completely
];

$mergedConfig = array_merge_recursive_distinct($config1, $config2);

echo "Original Config 1:
";
print_r($config1);
echo "
Original Config 2:
";
print_r($config2);
echo "
Merged Config (distinct):
";
print_r($mergedConfig);