Drupal 8 Module Development - Second Edition

Altering someone else's emails

Drupal is powerful not only because it allows us to add our own functionality but also because it allows us to alter existing functionality. An important vector for doing this is the alter hooks system. Remember these from Chapter 2, Creating Your First Module? These are hooks that are used to change the value of an array or object before it is used for whatever purpose it was going to be used for. When it comes to sending mails, we have an alter hook that allows us to change things on the mail definition before it goes out: hook_mail_alter(). For our module, we don't need to implement this hook. However, for the sake of making it complete, let's take a look at how we could use this hook to, for example, change ...