Laravel: Is this example of pessimistic locking correct?

I want to notify each user that has not been notified for one week.

The code looks like this:

// Select all users where attribute `notified` is older then one week
$users = \App\User::lastNotified(7)->get();

foreach($users as $user){
   $user->notifed = date('Y-m-d');
   \Mail::to($user)send(new NotificationMail($user));
   $user->save();
}

I want to make sure that if the code is executed parallel that each user will receive only one notification (no duplicates).

Have I understand it correctly that I have to use for this Pessimistic Locking like this:

DB::transaction(function () {
   $users = \App\User::lastNotified(7)->lockForUpdate()->get();

    foreach($users as $user){
       $user->notifed = date('Y-m-d');
       \Mail::to($user)send(new NotificationMail($user));
       $user->save();
    }
});

So if the the script is executed parallel, the slower script B would wait on line $users = \App\User::lastNotified(7)->lockForUpdate()->get(); until the quicker script A is done?

via Chebli Mohamed