function my_max(array $values): int {
    $max = $values[0];
    if(is_array($max)) {
        $max = my_max($max);
    }
    foreach ($values as $currentVal) {
        if (is_array($currentVal)) {
            $currentVal = my_max($currentVal);
        }
        if ($max < $currentVal) {
            $max = $currentVal;
        }
    }
    return $max;
}

echo my_max( array( array( array(5), 6 ), 3, 4 ) );
exit;