SMTP email sending class written in PHP

$smtpserver = "*****";
$smtpserverport = 25;
$smtpuser = "******";
$smtppass = "***** **";
$smtp = new smtp($smtpserver, $smtpserverport, true, $smtpuser, $smtppass); //A true here means that authentication is used, otherwise authentication is not used.
$smtp-> ;debug = false;
//$emailtype = "HTML";
for ($i=0; $i<5; $i++) {
 $smtp->sendmail("*****", "* *****", "Hello world!","This is only a test!");
}
echo "A total of $i emails were sent! ";
?>

The following is the implementation of the specific class.

class smtp {
    /* Public Variables */
    var $smtp_port;
    var $time_out;
    var $host_name;
    var $log_file;
    var $relay_host;
    var $debug;
    var $auth;
    var $user;
    var $pass;
    /* Private Variables */
    var $sock;
    /* Constractor */
    function smtp($relay_host = "", $smtp_port = 25, $auth = false, $user, $pass)
    {
        $this->debug = false;
        $this->smtp_port = $smtp_port;
        $this->relay_host = $relay_host;
        $this->time_out = 30; //is used in fsockopen()
        $this->auth = $auth; //auth
        $this->user = $user;
        $this->pass = $pass;
        $this->host_name = "localhost"; //is used in HELO command
        $this->log_file = "";
        $this->sock = false;
    }
    /* Main Function */
    function sendmail($to, $from, $subject = "", $body = "", $mailtype= "", $cc = "", $bcc = "", $additional_headers = "")
    {
        $mail_from = $this->get_address($this->strip_comment($from));
        $body = ereg_replace("(^|( ))(.)", "1.3", $body);
        $header .= "MIME-Version:1.0 ";
        if ($mailtype == "HTML") {
            $header .= "Content-Type:text/html ";
        }
        $header .= "To: " . $to . " ";
        if ($cc != "") {
            $header .= "Cc: " . $cc . " ";
        }
        $header .= "From: $from<" . $from . ">; ";
        $header .= "Subject: " . $subject . " ";
        $header .= $additional_headers;
        $header .= "Date: " . date("r") . " ";
        $header .= "X-Mailer:By Redhat (PHP/" . phpversion() . ") ";
        list($msec, $sec) = explode(" ", microtime());
        $header .= "Message-ID: <" . date("YmdHis", $sec) . "." . ($msec * 1000000) . "." . $mail_from . ">; ";
        $TO = explode(",", $this->strip_comment($to));
        if ($cc != "") {
            $TO = array_merge($TO, explode(",", $this->strip_comment($cc)));
        }
        if ($bcc != "") {
            $TO = array_merge($TO, explode(",", $this->strip_comment($bcc)));
        }
        $sent = true;
        foreach ($TO as $rcpt_to) {
            $rcpt_to = $this->get_address($rcpt_to);
            if (!$this->smtp_sockopen($rcpt_to)) {
                $this->log_write("Error: Cannot send email to " . $rcpt_to . " ");
                $sent = false;
                continue;
            }
            if ($this->smtp_send($this->host_name, $mail_from, $rcpt_to, $header, $body)) {
                $this->log_write("E-mail has been sent to <" . $rcpt_to . ">; ");
            } else {
                $this->log_write("Error: Cannot send email to <" . $rcpt_to . ">; ");
                $sent = false;
            }
            fclose($this->sock);
            $this->log_write("Disconnected from remote host ");
        }
        return $sent;
    }
    /* Private Functions */
    function smtp_send($helo, $from, $to, $header, $body = "")
    {
        if (!$this->smtp_putcmd("HELO", $helo)) {
            return $this->smtp_error("sending HELO command");
        }
        // auth
        if ($this->auth) {
            if (!$this->smtp_putcmd("AUTH LOGIN", base64_encode($this->user))) {
                return $this->smtp_error("sending HELO command");
            }
            if (!$this->smtp_putcmd("", base64_encode($this->pass))) {
                return $this->smtp_error("sending HELO command");
            }
        }
        if (!$this->smtp_putcmd("MAIL", "FROM:<" . $from . ">;")) {
            return $this->smtp_error("sending MAIL FROM command");
        }
        if (!$this->smtp_putcmd("RCPT", "TO:<" . $to . ">;")) {
            return $this->smtp_error("sending RCPT TO command");
        }
        if (!$this->smtp_putcmd("DATA")) {
            return $this->smtp_error("sending DATA command");
        }
        if (!$this->smtp_message($header, $body)) {
            return $this->smtp_error("sending message");
        }
        if (!$this->smtp_eom()) {
            return $this->smtp_error("sending ;;.;; [EOM]");
        }
        if (!$this->smtp_putcmd("QUIT")) {
            return $this->smtp_error("sending QUIT command");
        }
        return true;
    }
    function smtp_sockopen($address)
    {
        if ($this->relay_host == "") {
            return $this->smtp_sockopen_mx($address);
        } else {
            return $this->smtp_sockopen_relay();
        }
    }
    function smtp_sockopen_relay()
    {
        $this->log_write("Trying to " . $this->relay_host . ":" . $this->smtp_port . " ");
        $this->sock = @fsockopen($this->relay_host, $this->smtp_port, $errno, $errstr, $this->time_out);
        if (!($this->sock && $this->smtp_ok())) {
            $this->log_write("Error: Cannot connenct to relay host " . $this->relay_host . " ");
            $this->log_write("Error: " . $errstr . " (" . $errno . ") ");
            return false;
        }
        $this->log_write("Connected to relay host " . $this->relay_host . " ");
        return true;;
    }
    function smtp_sockopen_mx($address)
    {
        $domain = ereg_replace("^.+@([^@]+)$", "1", $address);
        if (!@getmxrr($domain, $MXHOSTS)) {
            $this->log_write("Error: Cannot resolve MX "" . $domain . "" ");
            return false;
        }
        foreach ($MXHOSTS as $host) {
            $this->log_write("Trying to " . $host . ":" . $this->smtp_port . " ");
            $this->sock = @fsockopen($host, $this->smtp_port, $errno, $errstr, $this->time_out);
            if (!($this->sock && $this->smtp_ok())) {
                $this->log_write("Warning: Cannot connect to mx host " . $host . " ");
                $this->log_write("Error: " . $errstr . " (" . $errno . ") ");
                continue;
            }
            $this->log_write("Connected to mx host " . $host . " ");
            return true;
        }
        $this->log_write("Error: Cannot connect to any mx hosts (" . implode(", ", $MXHOSTS) . ") ");
        return false;
    }
    function smtp_message($header, $body)
    {
        fputs($this->sock, $header . " " . $body);
        $this->smtp_debug(">; " . str_replace(" ", " " . ">; ", $header . " >; " . $body . " >; "));
        return true;
    }
    function smtp_eom()
    {
        fputs($this->sock, " . ");
        $this->smtp_debug(". [EOM] ");
        return $this->smtp_ok();
    }
    function smtp_ok()
    {
        $response = str_replace(" ", "", fgets($this->sock, 512));
        $this->smtp_debug($response . " ");
        if (!ereg("^[23]", $response)) {
            fputs($this->sock, "QUIT ");
            fgets($this->sock, 512);
            $this->log_write("Error: Remote host returned "" . $response . "" ");
            return false;
        }
        return true;
    }
    function smtp_putcmd($cmd, $arg = "")
    {
        if ($arg != "") {
            if ($cmd == "") $cmd = $arg;
            else $cmd = $cmd . " " . $arg;
        }
        fputs($this->sock, $cmd . " ");
        $this->smtp_debug(">; " . $cmd . " ");
        return $this->smtp_ok();
    }
    function smtp_error($string)
    {
        $this->log_write("Error: Error occurred while " . $string . ". ");
        return false;
    }
    function log_write($message)
    {
        $this->smtp_debug($message);
        if ($this->log_file == "") {
            return true;
        }
        $message = date("M d H:i:s ") . get_current_user() . "[" . getmypid() . "]: " . $message;
        if (!@file_exists($this->log_file) || !($fp = @fopen($this->log_file, "a"))) {
            $this->smtp_debug("Warning: Cannot open log file "" . $this->log_file . "" ");
            return false;;
        }
        flock($fp, LOCK_EX);
        fputs($fp, $message);
        fclose($fp);
        return true;
    }
    function strip_comment($address)
    {
        $comment = "([^()]*)";
        while (ereg($comment, $address)) {
            $address = ereg_replace($comment, "", $address);
        }
        return $address;
    }
    function get_address($address)
    {
        $address = ereg_replace("([ ])+", "", $address);
        $address = ereg_replace("^.*<(.+)>;.*$", "1", $address);
        return $address;
    }
    function smtp_debug($message)
    {
        if ($this->debug) {
            echo $message . ";";
        }
    }
}
?>