Plugins

Plugins are provided with Swift Mailer and can be used to extend the behavior of the library in situations where using simple class inheritance would be more complex.

AntiFlood Plugin

Many SMTP servers have limits on the number of messages that may be sent during any single SMTP connection. The AntiFlood plugin provides a way to stay within this limit while still managing a large number of emails.

A typical limit for a single connection is 100 emails. If the server you connect to imposes such a limit, it expects you to disconnect after that number of emails has been sent. You could manage this manually within a loop, but the AntiFlood plugin provides the necessary wrapper code so that you don't need to worry about this logic.

Regardless of limits imposed by the server, it's usually a good idea to be conservative with the resources of the SMTP server. Sending will become sluggish if the server is being over-used so using the AntiFlood plugin will not be a bad idea even if no limits exist.

The AntiFlood plugin's logic is basically to disconnect and the immediately re-connect with the SMTP server every X number of emails sent, where X is a number you specify to the plugin.

You can also specify a time period in seconds that Swift Mailer should pause for between the disconnect/re-connect process. It's a good idea to pause for a short time (say 30 seconds every 100 emails) simply to give the SMTP server a chance to process its queue and recover some resources.

Using the AntiFlood Plugin

The AntiFlood Plugin -- like all plugins -- is added with the Mailer class's registerPlugin() method. It takes two constructor parameters: the number of emails to pause after, and optionally the number of seconds to pause for.

To use the AntiFlood plugin:

  • Create an instance of the Mailer using any Transport you choose.
  • Create an instance of the Swift_Plugins_AntiFloodPlugin class, passing in one or two constructor parameters.
  • Register the plugin using the Mailer's registerPlugin() method.
  • Continue using Swift Mailer to send messages as normal.

When Swift Mailer sends messages it will count the number of messages that have been sent since the last re-connect. Once the number hits your specified threshold it will disconnect and re-connect, optionally pausing for a specified amount of time.

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require_once 'lib/swift_required.php';

// Create the Mailer using any Transport
$mailer = Swift_Mailer::newInstance(
  Swift_SmtpTransport::newInstance('smtp.example.org', 25)
);

// Use AntiFlood to re-connect after 100 emails
$mailer->registerPlugin(new Swift_Plugins_AntiFloodPlugin(100));

// And specify a time in seconds to pause for (30 secs)
$mailer->registerPlugin(new Swift_Plugins_AntiFloodPlugin(100, 30));

// Continue sending as normal
for ($lotsOfRecipients as $recipient) {
  ...

  $mailer->send( ... );
}

Throttler Plugin

If your SMTP server has restrictions in place to limit the rate at which you send emails, then your code will need to be aware of this rate-limiting. The Throttler plugin makes Swift Mailer run at a rate-limited speed.

Many shared hosts don't open their SMTP servers as a free-for-all. Usually they have policies in place (probably to discourage spammers) that only allow you to send a fixed number of emails per-hour/day.

The Throttler plugin supports two modes of rate-limiting and with each, you will need to do that math to figure out the values you want. The plugin can limit based on the number of emails per minute, or the number of bytes-transferred per-minute.

Using the Throttler Plugin

The Throttler Plugin -- like all plugins -- is added with the Mailer class' registerPlugin() method. It has two required constructor parameters that tell it how to do its rate-limiting.

To use the Throttler plugin:

  • Create an instance of the Mailer using any Transport you choose.
  • Create an instance of the Swift_Plugins_ThrottlerPlugin class, passing the number of emails, or bytes you wish to limit by, along with the mode you're using.
  • Register the plugin using the Mailer's registerPlugin() method.
  • Continue using Swift Mailer to send messages as normal.

When Swift Mailer sends messages it will keep track of the rate at which sending messages is occurring. If it realises that sending is happening too fast, it will cause your program to sleep() for enough time to average out the rate.

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require_once 'lib/swift_required.php';

// Create the Mailer using any Transport
$mailer = Swift_Mailer::newInstance(
  Swift_SmtpTransport::newInstance('smtp.example.org', 25)
);

// Rate limit to 100 emails per-minute
$mailer->registerPlugin(new Swift_Plugins_ThrottlerPlugin(
  100, Swift_Plugins_ThrottlerPlugin::MESSAGES_PER_MINUTE
));

// Rate limit to 10MB per-minute
$mailer->registerPlugin(new Swift_Plugins_ThrottlerPlugin(
  1024 * 1024 * 10, Swift_Plugins_ThrottlerPlugin::BYTES_PER_MINUTE
));

// Continue sending as normal
for ($lotsOfRecipients as $recipient) {
  ...

  $mailer->send( ... );
}

Logger Plugin

The Logger plugins helps with debugging during the process of sending. It can help to identify why an SMTP server is rejecting addresses, or any other hard-to-find problems that may arise.

The Logger plugin comes in two parts. There's the plugin itself, along with one of a number of possible Loggers that you may choose to use. For example, the logger may output messages directly in realtime, or it may capture messages in an array.

One other notable feature is the way in which the Logger plugin changes Exception messages. If Exceptions are being thrown but the error message does not provide conclusive information as to the source of the problem (such as an ambiguous SMTP error) the Logger plugin includes the entire SMTP transcript in the error message so that debugging becomes a simpler task.

There are a few available Loggers included with Swift Mailer, but writing your own implementation is incredibly simple and is achieved by creating a short class that implements the Swift_Plugins_Logger interface.

  • Swift_Plugins_Loggers_ArrayLogger: Keeps a collection of log messages inside an array. The array content can be cleared or dumped out to the screen.
  • Swift_Plugins_Loggers_EchoLogger: Prints output to the screen in realtime. Handy for very rudimentary debug output.

Using the Logger Plugin

The Logger Plugin -- like all plugins -- is added with the Mailer class' registerPlugin() method. It accepts an instance of Swift_Plugins_Logger in its constructor.

To use the Logger plugin:

  • Create an instance of the Mailer using any Transport you choose.
  • Create an instance of the a Logger implementation of Swift_Plugins_Logger.
  • Create an instance of the Swift_Plugins_LoggerPlugin class, passing the created Logger instance to its constructor.
  • Register the plugin using the Mailer's registerPlugin() method.
  • Continue using Swift Mailer to send messages as normal.
  • Dump the contents of the log with the logger's dump() method.

When Swift Mailer sends messages it will keep a log of all the interactions with the underlying Transport being used. Depending upon the Logger that has been used the behaviour will differ, but all implementations offer a way to get the contents of the log.

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require_once 'lib/swift_required.php';

// Create the Mailer using any Transport
$mailer = Swift_Mailer::newInstance(
 Swift_SmtpTransport::newInstance('smtp.example.org', 25)
);

// To use the ArrayLogger
$logger = new Swift_Plugins_Loggers_ArrayLogger();
$mailer->registerPlugin(new Swift_Plugins_LoggerPlugin($logger));

// Or to use the Echo Logger
$logger = new Swift_Plugins_Loggers_EchoLogger();
$mailer->registerPlugin(new Swift_Plugins_LoggerPlugin($logger));

// Continue sending as normal
for ($lotsOfRecipients as $recipient) {
 ...

 $mailer->send( ... );
}

// Dump the log contents
// NOTE: The EchoLogger dumps in realtime so dump() does nothing for it
echo $logger->dump();

Decorator Plugin

Often there's a need to send the same message to multiple recipients, but with tiny variations such as the recipient's name being used inside the message body. The Decorator plugin aims to provide a solution for allowing these small differences.

The decorator plugin works by intercepting the sending process of Swift Mailer, reading the email address in the To: field and then looking up a set of replacements for a template.

While the use of this plugin is simple, it is probably the most commonly misunderstood plugin due to the way in which it works. The typical mistake users make is to try registering the plugin multiple times (once for each recipient) -- inside a loop for example. This is incorrect.

The Decorator plugin should be registered just once, but containing the list of all recipients prior to sending. It will use this list of recipients to find the required replacements during sending.

Using the Decorator Plugin

To use the Decorator plugin, simply create an associative array of replacements based on email addresses and then use the mailer's registerPlugin() method to add the plugin.

First create an associative array of replacements based on the email addresses you'll be sending the message to.

Note

The replacements array becomes a 2-dimensional array whose keys are the email addresses and whose values are an associative array of replacements for that email address. The curly braces used in this example can be any type of syntax you choose, provided they match the placeholders in your email template.

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$replacements = array();
foreach ($users as $user) {
  $replacements[$user['email']] = array(
    '{username}'=>$user['username'],
    '{password}'=>$user['password']
  );
}

Now create an instance of the Decorator plugin using this array of replacements and then register it with the Mailer. Do this only once!

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$decorator = new Swift_Plugins_DecoratorPlugin($replacements);

$mailer->registerPlugin($decorator);

When you create your message, replace elements in the body (and/or the subject line) with your placeholders.

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$message = Swift_Message::newInstance()
  ->setSubject('Important notice for {username}')
  ->setBody(
    "Hello {username}, we have reset your password to {password}\n" .
    "Please log in and change it at your earliest convenience."
  )
  ;

foreach ($users as $user) {
  $message->addTo($user['email']);
}

When you send this message to each of your recipients listed in your $replacements array they will receive a message customized for just themselves. For example, the message used above when received may appear like this to one user:

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Subject: Important notice for smilingsunshine2009

Hello smilingsunshine2009, we have reset your password to rainyDays
Please log in and change it at your earliest convenience.

While another use may receive the message as:

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Subject: Important notice for billy-bo-bob

Hello billy-bo-bob, we have reset your password to dancingOctopus
Please log in and change it at your earliest convenience.

While the decorator plugin provides a means to solve this problem, there are various ways you could tackle this problem without the need for a plugin. We're trying to come up with a better way ourselves and while we have several (obvious) ideas we don't quite have the perfect solution to go ahead and implement it. Watch this space.

Providing Your Own Replacements Lookup for the Decorator

Filling an array with replacements may not be the best solution for providing replacement information to the decorator. If you have a more elegant algorithm that performs replacement lookups on-the-fly you may provide your own implementation.

Providing your own replacements lookup implementation for the Decorator is simply a matter of passing an instance of Swift_Plugins_Decorator_Replacements to the decorator plugin's constructor, rather than passing in an array.

The Replacements interface is very simple to implement since it has just one method: getReplacementsFor($address).

Imagine you want to look up replacements from a database on-the-fly, you might provide an implementation that does this. You need to create a small class.

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class DbReplacements implements Swift_Plugins_Decorator_Replacements {
  public function getReplacementsFor($address) {
    $sql = sprintf(
      "SELECT * FROM user WHERE email = '%s'",
      mysql_real_escape_string($address)
    );

    $result = mysql_query($sql);

    if ($row = mysql_fetch_assoc($result)) {
      return array(
        '{username}'=>$row['username'],
        '{password}'=>$row['password']
      );
    }
  }
}

Now all you need to do is pass an instance of your class into the Decorator plugin's constructor instead of passing an array.

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$decorator = new Swift_Plugins_DecoratorPlugin(new DbReplacements());

$mailer->registerPlugin($decorator);

For each message sent, the plugin will call your class' getReplacementsFor() method to find the array of replacements it needs.

Note

If your lookup algorithm is case sensitive, you should transform the $address argument as appropriate -- for example by passing it through strtolower().

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Creative Commons License Swiftmailer documentation is licensed under a Creative Commons Attribution-Share Alike 3.0 Unported License.