add field in joomla contact form of attach file - joomla

Question

Please Help me i am using joomla v 3 i am trying to add field in in contact form i have set all code in joomla files but attached files not receiving? please see code below.
$filename = $data['filename'];
$name = $data['contact_name'];
$subject = $data['contact_subject'];
$body = $data['contact_message'];
$mime_boundary = "==Multipart_Boundary_x" . md5(mt_rand()) . "x";
// Now Store the file information to a variables for easier access
$tmp_name = $_FILES['filename']['tmp_name'];
$type = $_FILES['filename']['type'];
$file_name = $_FILES['filename']['name'];
$size = $_FILES['filename']['size'];
// Now here we setting up the message of the mail
$message = "\n\n Here is your file: $file_name";
if (file_exists($tmp_name)) {
if (is_uploaded_file($tmp_name)) {
$file = fopen($tmp_name, 'rb');
$data = fread($file, filesize($tmp_name));
fclose($file);
$data = chunk_split(base64_encode($data));
}
$headers = "From: $body\r\n" .
"MIME-Version: 1.0\r\n" .
"Content-Type: multipart/mixed;\r\n" .
" boundary=\"{$mime_boundary}\"";
$message = "This is a multi-part message in MIME format.\n\n" .
"--{$mime_boundary}\n" .
"Content-Type: text/plain; charset=\"iso-8859-1\"\n" .
"Content-Transfer-Encoding: 7bit\n\n" .
$message . "\n\n";
// Now we'll insert a boundary to indicate we're starting the attachment we have to specify the content type, file name, and disposition as an attachment, then add the file content and set another boundary to indicate that the end of the file has been reached
$message .= "--{$mime_boundary}\n" .
"Content-Type: {$type};\n" .
" name=\"{$file_name}\"\n" .
//"Content-Disposition: attachment;\n" .
//" filename=\"{$fileatt_name}\"\n" .
"Content-Transfer-Encoding: base64\n\n" .
$data . "\n\n" .
"--{$mime_boundary}--\n";
}
// Prepare email body
$body = $prefix . "\n" . $name . ' <' . $email . '>' . "\n" . $filename . "\r\n\r\n" . stripslashes($body);
$mail = JFactory::getMailer();
$mail->addRecipient($contact->email_to);
$mail->addReplyTo(array($email, $name));
$mail->setSender(array($mailfrom, $fromname));
$mail->setSubject($sitename . ': ' . $subject);
$mail->setBody($body, $headers);
$sent = $mail->Send();
file name is receiving in body i have set but file not receiving in mail.
i have set <input type="file" name="filename"/>
please check it for me