Making PHP's mail() asynchronous

I have PHP's mail() using ssmtp which doesn't have a queue/spool, and is synchronous with AWS SES.

I heard I could use SwiftMail to provide a spool, but I couldn't work out a simple recipe to use it like I do currently with mail().

I want the least amount of code to provide asynchronous mail. I don't care if the email fails to send, but it would be nice to have a log.

Any simple tips or tricks? Short of running a full blown mail server? I was thinking a sendmail wrapper might be the answer but I couldn't work out nohup.

php-fpm

You must run php-fpm for fastcgi_finish_request to be available.

echo "I get output instantly";
fastcgi_finish_request(); // Close and flush the connection.
sleep(10); // For illustrative purposes. Delete me.
mail("test@example.org", "lol", "Hi");

It's pretty easy queuing up any arbitrary code to processed after finishing the request to the user:

$post_processing = [];
/* your code */
$email = "test@example.org";
$subject = "lol";
$message = "Hi";

$post_processing[] = function() use ($email, $subject, $message) {
  mail($email, $subject, $message);
};

echo "Stuff is going to happen.";

/* end */

fastcgi_finish_request();

foreach($post_processing as $function) {
  $function();
}

Hipster background worker

Instantly time-out a curl and let the new request deal with it. I was doing this on shared hosts before it was cool. (it's never cool)

if(!empty($_POST)) {
  sleep(10);
  mail($_POST['email'], $_POST['subject'], $_POST['message']);
  exit(); // Stop so we don't self DDOS.
}

$ch = curl_init("http://" . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']);

curl_setopt($ch, CURLOPT_TIMEOUT, 1);
curl_setopt($ch, CURLOPT_NOSIGNAL, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, [
  'email' => 'noreply@example.org',
  'subject' => 'foo',
  'message' => 'bar'
]);

curl_exec($ch);
curl_close($ch);

echo "Expect an email in 10 seconds.";