You can follow the article lah.
http://www.phpbuilder.com/columns/kartic20000807.php3
and you can download the sample code.
you can use the class in this simple way:
$message=" .........";
include 'mime.class';
$str = 'title';
$mime = new MIME_mail($reply_email, $send_address, $str);
$mime->attach($message, '', HTML, BASE64);
$mime->attach($textmessage, '', TEXT, QP);
$mime->send_mail();