PHP - Send Mail With Attachments.

Hello,
i have this code for sending email it works great but i don't know where to start in sending emails with a pdf file attached ex: test.pdf. Any suggestions?

 <?php
    session_start();
    require_once('framework/framework.php');
    include('framework/class.smtp.inc');

//--- databse settings

    $dsn = array(
        'dbtype'      => 'mysql',
        'username'     => '',
        'password'     => '',
        'host'         => '',
        'database'  => ''
    );
    
    try {
        $db = db::connect($dsn);
    }
    catch (Exception $e) { 
        die($e->getMessage()); 
    }
    
//---

    $subject="Formular online pentru participantii Diaspora Stiintifica 2010";

// +--------------  BEGIN  ----  Functia de trimitere mail prin smtp  -------------------+ */

    function trimite($destinatar='', $subiect='', $mesaj='') {

//--- mail settings
    $smtp_server_host="mail.server.com";
    $smtp_server_port="25";
    $sender="email@email.com";
    $return_path="email@email.com";
    $smtp_username="email@email.com";
    $smtp_pswd="123";
        /***************************************
        ** Setup some parameters which will be
        ** passed to the smtp::connect() call.
        ***************************************/
        $params['host'] = $smtp_server_host;    // The smtp server host/ip
        $params['port'] = $smtp_server_port;    // The smtp server port
        $params['helo'] = exec('hostname');        // What to use when sending the helo command. Typically, your domain/hostname
        $params['auth'] = false;                    // Whether to use basic authentication or not
//        $params['user'] = $smtp_username;        // Username for authentication
//        $params['pass'] = $smtp_pswd;            // Password for authentication
        $params['timeout'] = '60';
        /***************************************
        ** These parameters get passed to the
        ** smtp->send() call.
        ***************************************/
        $send_params['recipients']    = $destinatar;    // The recipients (can be multiple)
        $send_params['headers']        = array( "MIME-Version: 1.0", 
                                            "X-Mailer: PHP/" . phpversion(),
                                            "Return-Path: ".$return_path,
                                            "From: ".$sender,
                                            "To: ".$destinatar,
                                            "Subject: ".$subiect,
                                            "Content-type: text/html; charset=UTF-8",
                                            "Content-Transfer-Encoding: 8bit");
        $send_params['from']        = $sender;    // This is used as in the MAIL FROM: cmd
                                                // It should end up as the Return-Path: header
        $send_params['body'] = $mesaj;

        /***************************************
        ** The code that creates the object and
        ** sends the email.
        ***************************************/
        $smtp = new smtp($params);
        $smtp->connect();
        $trimis=$smtp->send($send_params);
        $raspuns=array($destinatar, $trimis, $smtp->errors);
        //    $smtp->rset();
    
//--- Bcc:
/*        $send_params['recipients']    = $sender;
        $trimisi=$smtp->send($send_params);
        $errmsgi=$smtp->errors;
        print "<br>bcc: ".$send_params['recipients']."; ".$trimisi."<br>";
            for ($n = 0 ; $n <= count($errmsgi) - 1; $n++) {
                print "<br>"."&nbsp;&nbsp;bccerr: &nbsp;<strong>".$errmsgi[$n]."</strong><br>";
            }
*/
        $smtp->quit();
        return $raspuns;
    }
// +--------------   END   ----  Functia de trimitere mail prin smtp  -------------------+ */


// +---------------------------------------------------------------------------+

    $afisez = "";
    $cond=0;
    
    $query = "SELECT email_1 FROM inregistrari WHERE `completat`=0";
    $useri = $db->getAll($query);
    $i=0;
    $j=0;
    $k=0;
    
    foreach ($useri as $row) {
        $tpl = new HTML_Template_Sigma('mesaj');
        $tpl->loadTemplateFile("mesaj.html");
        $tpl->setVariable($row);
        $html=$tpl->get(); //*/
        $html=nl2br($html);
        $html=str_replace(chr(10), "", $html);
        $html=str_replace(chr(13), "", $html); // */

// +----------------------+
        $subiect = $subject;
        if (!empty($row['email_1'])) {
            $subelements=preg_split("/, /", $row['email_1'], -1, PREG_SPLIT_NO_EMPTY);
            for ($m = 0 ; $m <= count($subelements) - 1; $m++) {

                $rez = trimite($subelements[$m], $subiect, $html);
                if ($rez[1]==true) {
                    $afisez .= $rez[0].";1<br>";
                    $i++;
                } else {
                    $afisez .= $rez[0].";0<br>";
                    $errmsg=$rez[2];
                    for ($n = 0 ; $n <= count($errmsg) - 1; $n++) {
                        $afisez .= "&nbsp;&nbsp;&nbsp;&nbsp;<strong>".$errmsg[$n]."</strong><br>";
                    }
                    $j++;
                }
            }
        } else {
            $afisez .= $row['email_1'].";no email;n<br>";
            $k++;
        }
    }
$afisez .= "<br>{$i} mesaje Trimise<br>";
$afisez .= "{$j} mesaje Netrimise<br>";
$afisez .= "{$k} mesaje fara adresa<br>";
print $afisez;
?>