function dirFinder ($folder)
{
    $all_in_folder = scandir($folder);
    foreach ($all_in_folder as $object) {
        if ($object == '.' || $object == '..') continue;
        $path_to_object = "$folder" . DIRECTORY_SEPARATOR . "$object";
        if (is_dir($path_to_object)) {
            yield $path_to_object;
            dirFinder($path_to_object);
        }
    }
}

foreach (dirFinder('C:Test') as $value) {
    echo $value . '<br />';
}