PHP: send multi attachment emails with swiftmailer

gistfile1.php

<?php
require_once('swift/lib/swift_required.php');

$email = $_POST['email'];
$subject = "my subject";
$user_message = "<b>message body</b>";

$mailer = new Swift_Mailer(new Swift_MailTransport());
$message = Swift_Message::newInstance();
$message->setSubject($subject);
$message->setFrom(array($email));
$message->setTo(array('[email protected]'));
$message->setCc(array('[email protected]'));
$message->setBody($user_message, 'text/html');

for ($i=0; $i < count($_FILES['attachment']); $i++) { 
	$target_path = "uploads/" . basename($_FILES['attachment']['name'][$i]);
	if( move_uploaded_file($_FILES['attachment']['tmp_name'][$i], $target_path) ) {
		$message->attach(Swift_Attachment::fromPath($target_path));

                //if we don't want to keep the image
                unlink($target_path);
	}
}

$mailer->send($message);
header("location:thank_you.html");
?>

Is there a way to select one image/file at a time in Swiftmailer? i.e. Open the File Upload/Windows Explorer and double click the file then re-open the File Upload/Windows Explorer and select another file, thus appending to the array of attachments?