Drupal 7 Module Development

Building an Admin Interface
Implementing hook_mail()
In the last section, when we called drupal_mail(), we indicated that it should
invoke hook_mail() in the user_warn module. This means that Drupal will be
looking for a function named user_warn_mail(). This function is as follows:
/**
* Implement hook_mail().
*/
function user_warn_mail($key, &$message, $params) {
switch ($key) {
case 'warn':
$account = $params['account'];
$subject = variable_get('user_warn_e-mail_subject',
'Administrative Warning');
$body = variable_get('user_warn_e-mail_text',
'You\'ve been warned!');
if (variable_get('user_warn_bcc', FALSE)) {
$admin_mail = variable_get('site_mail', NULL);
$message['headers']['bcc'] = $admin_mail;
}
}
}
$message['to'] = $account->mail;
$message['subject'] = $subject;
$message['body'][] = $body;
break;
As you can see the preceding function receives three arguments:
• The key we passed in parameter two of our call to drupal_mail(),
indicating what message should be sent.
• The structured array that Drupal creates to represent an e-mail message.
At this point this array has already been populated with the mail's default
header information.
• The data we passed from drupal_mail() in the $params argument (in this
case, a user's account object.)
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