simple mailing system with symfony - part I

This article is the beginning of a tutorial presenting an easy way to implement database-templated-mailing system for symfony projects.

the basics

The basic version uses 2 tables: mail_queue and mail_template. For each type of mails, one template object is created.

mail_template

name, description - name & description of the template
template_code - (HTML, including variables marked as {variable})
template_data - what variables are defined, just a description, no calculations performed


For each single mail to be sent, one queue object is created.

mail_queue

template_id - which template to use
mail_data - serialized array: variables=>values
mail_recipent - formatted/serialized recipent information
mail_author - as above
mail_subject - string
send_at - time that this email should be sent
sent - boolean, already sent

E-mail is sent when sent=0 (and marked 1 afterwards, not to be sent again; in case of errors - mark as 2) and when actual time has gone beyond send_at. send_at column is especially useful, as you may create emails in a long time advance. For example, you want to send a reminder E-mail: create a new MailQueue object with its datetime value equal to current timestamp + two weeks. This would make the E-mail to be sent in two weeks time from now.

example usage

What kind of mails can we define? It depends on your project functionalities. For example, if your project is a stock managing software that stores information about products and their states, you can send important E-mails when one of the following situations take place:

• status of a product is changing - other employees shall be informed about that,
• quantity of a product reached alarming level - supply needed immediately,
• inform customers when product becomes available again,
• and so on...

A template object is created for each of the situations defined above. There's a MailTools class with static methods processing mail sending. Just like notifyProductStatusHasChanged method, taking two parameters: Product and status change. This method creates a mail_queue instance, defining specific data for this type of E-mail, using Article object passed as the parameter.

some details on implementation

Symfony Swift Mailer integration is provided with a ready to use mail queueing system. However, I decided to create a special task, defined to send E-mails that are marked with sent=0. The code is pretty obvious:

$mails = Doctrine::getTable('MailQueue')
  ->getMails2bSentQuery()
  ->execute();
 
foreach($mails as $m)
{
  $m->send();
}

Above task is run by a cron job (every few minutes). getMails2bSentQuery method looks for MailQueue objects that have sent=0 and send_at <= now. For each of those objects, the template code (HTML) is filled with variable data and sent afterwards. The mail data is unserialized first and each variable is injected into the HTML code using str_replace function:

protected function generateContent()
{
  $code = $this->getTemplate()->getTemplateCode();
  $data = unserialize($this->getMailData());
  foreach($data as $key => $value)
    $code = str_replace('{'.$key.'}', $value, $code);
  return $code;
}

Each mail template is defined using HTML/CSS code. It works similar to smarty template engine. Just define a list of variables of and all occurences of {VARIABLE} will be replaced with the parameter value you pass.

to be continued

This was just a brief overview. In the near future, precise code examples will be provided in tutorial's part 2.