Trouble getting file attachment to work with Swiftmailer - php

Question

I am trying to use swiftmailer to upload a file from a form, but I still get an error.
I really don't know where I'm going wrong. Any help and explanation would be greatly appreciated.
index.html
<form method="post" action="mail.php" enctype="multipart/form-data">
Attach a file: <input type="file" id="attachment" name="attachment">
<button type="submit">SUBMIT</button>
</form>
mail.php (correct)
Then it imports mail_sender.php
mail_sender.php
<?php
$file = 'attachment/'.basename($_FILES['attachment']['name']);
$upload = move_uploaded_file($_FILES['attachment']['tmp_name'],$file);
if(isset($timeZone) && $timeZone != ""){
date_default_timezone_set($timeZone);
}
else{
date_default_timezone_set("UTC");
}
// Require the Swift Mailer library
require_once 'swift_required.php';
$messageText = "";
if($emailMethod == 'phpmail'){
$transport = Swift_MailTransport::newInstance();
}elseif($emailMethod == 'smtp'){
$transport = Swift_SmtpTransport::newInstance( $outgoingServerAddress, $outgoingServerPort, $outgoingServerSecurity )
->setUsername( $sendingAccountUsername )
->setPassword( $sendingAccountPassword );
}
$mailer = Swift_Mailer::newInstance($transport);
// Creating the message text using fields sent through POST
foreach ($_POST as $key => $value)
{
// Sets of checkboxes will be shown as comma-separated values as they are passed in as an array.
if(is_array($value)){
$value = implode(', ' , $value);
}
$messageText .= ucfirst($key).": ".$value."\n\n";
}
if(isset($_POST['email']) && isset($_POST['name']) ){
$fromArray = array($_POST['email'] => $_POST['name']);
}else{ $fromArray = array($sendingAccountUsername => $websiteName); }
$message = Swift_Message::newInstance($emailSubject)
->setFrom($fromArray)
->addPart(strip_tags($messageText), 'application/pdf')
->attach(Swift_Attachment::fromPath($file))
->setTo(array($recipientEmail => $recipientName))->setBody($messageText, 'text/html');
}
// Send the message or catch an error if it occurs.
try{
echo($mailer->send($message));
}
catch(Exception $e){
echo($e->getMessage());
}
exit;
?>
Thanks in advance