这有个例子：

/*
*  Class mime_mail
*  Original implementation by Sascha Schumann <sascha@schumann.cx>
*  Modified by Tobias Ratschiller <tobias@dnet.it>:
*      - General code clean-up
*      - separate body- and from-property
*      - killed some mostly un-necessary stuff
*/

class mime_mail
{
var $parts;
var $to;
var $from;
var $headers;
var $subject;
var $body;

/*
  *     void mime_mail()
  *     class constructor
  */
function mime_mail()
  {
  $this->parts = array();
  $this->to = "";
  $this->from = "";
  $this->subject = "";
  $this->body = "";
  $this->headers = "";
  }

/*
  *     void add_attachment(string message, [string name], [string ctype])
  *     Add an attachment to the mail object
  */
function add_attachment($message, $name = "", $ctype =
"application/octet-stream")
  {
  $this->parts[] = array (
                          "ctype" => $ctype,
                          "message" => $message,
                          "encode" => $encode,
                          "name" => $name
                          );
  }

/*
*      void build_message(array part=
*      Build message parts of an multipart mail
*/
function build_message($part)
{
$message = $part["message"];
$message = chunk_split(base64_encode($message));
$encoding = "base64";
return "Content-Type: ".$part["ctype"].
                        ($part["name"]?"; name=\"".$part["name"]."\"":"").
                        "\nContent-Transfer-Encoding: $encoding".
            "\nContent-Disposition: inline".
            ($part["name"]?"; filename=\"".$part["name"]."\"":"").
            "\n\n$message\n";
}

/*
*      void build_multipart()
*      Build a multipart mail
*/
function build_multipart()
{
$boundary = "b".md5(uniqid(time()));
$mult