Anti Spam Protection

Hi.. I found nice piece of code.. but I think.. it not works with PunBB 1.3. Can somebody try to change for usability in the (punbb 1.3) post.php file?

    // Deny words
    $words = array(
    "pxxn",
    "rxxg",
    "axxl",
    "sxx" );

    foreach($words as $word)
    {
    if ($stristr($message, $words) !== false))
    $errors[] = $lang_post['Forbidden words in post. Access denied'];
    } 

Founded at URL scriptol.com/how-to/insert-adsense-in-punbb-forum.php with instruction how to use - but not works with 1.3. Thank you.