First you need to include the “swift_required.php” file, then you create an instance of the Mailer using any of the Transports (probably Swift_SmtpTransport, Swift_SendmailTransport or Swift_MailTransport). Then you create a a message, add some parts to it and send it with the Mailer.

<?php
 
//Include this needed file
require_once '/path/to/swift/lib/swift_required.php';
 
//Start the mailer
$mailer = new Swift_Mailer(new Swift_SendmailTransport('/usr/sbin/sendmail -oi -t'));
 
//Create a message
$message = Swift_Message::newInstance('Your subject')
  ->addPart('Your text message', 'text/plain')
  ->addPart('Your HTML message', 'text/html')
  ->setFrom(array('your@address.tld' => 'Your Name'))
  ->setTo(array('someone@address.tld' => 'Person name'));
 
//Send it
$mailer->send($message);

Now would probably be a good time to introduce the concept of “everything’s an attachment”. Users of version 3 will be familiar with this, but you can also add mime parts in this way:

$message = Swift_Message::newInstance('Your subject')
  ->attach(new Swift_MimePart('Your text message', 'text/plain'))
  ->attach(new Swift_MimePart('Your HTML message', 'text/html'))
  ->setFrom(array('your@address.tld' => 'Your Name'))
  ->setTo(array('someone@address.tld' => 'Person name'));

Swift knows how to attach a mime part to the message.

Finally, you can add one part just like you’re sending a basic message, then attach your alternative part:

$message = Swift_Message::newInstance('Your subject', 'Your HTML message', 'text/html')
  ->addPart('Your text message', 'text/plain')
  ->setFrom(array('your@address.tld' => 'Your Name'))
  ->setTo(array('someone@address.tld' => 'Person name'));

All three approaches yield the same end result. I’d prefer the first example over the second two, but understanding how you can “compose” a message by attaching things to it will help you to grasp some other concepts later on ;)