static public function generatePassword($length = 32, $add_dashes = false, $available_sets = 'lud')
    {
        $sets = array();
        if (strpos($available_sets, 'l') !== false)
            $sets[] = 'abcdefghjkmnpqrstuvwxyz';
        if (strpos($available_sets, 'u') !== false)
            $sets[] = 'ABCDEFGHJKMNPQRSTUVWXYZ';
        if (strpos($available_sets, 'd') !== false)
            $sets[] = '123456789';
        if (strpos($available_sets, 's') !== false)
            $sets[] = '!@#$%&*?';

        $all = '';
        $password = '';
        foreach ($sets as $set) {
            $password .= $set[array_rand(str_split($set))];
            $all .= $set;
        }

        $all = str_split($all);
        for ($i = 0; $i < $length - count($sets); $i++)
            $password .= $all[array_rand($all)];

        $password = str_shuffle($password);

        if (!$add_dashes)
            return $password;

        $dash_len = floor(sqrt($length));
        $dash_str = '';
        while (strlen($password) > $dash_len) {
            $dash_str .= substr($password, 0, $dash_len) . '-';
            $password = substr($password, $dash_len);
        }
        $dash_str .= $password;
        return $dash_str;
    }