/**
  * Sends an email with a link, for verifying the given email address.
  * @param integer $id
  * @return boolean whether the email was send
  */
 public function sendActivityFollowersEmail($id)
 {
     $projectActivity = ProjectActivity::findOne($id);
     $project = $projectActivity->project;
     $userIds = explode(',', $projectActivity->followers->usersFollowing);
     foreach ($userIds as $userId) {
         $user = User::findOne($userId);
         if ($user) {
             \Yii::$app->mailer->compose('emailActivityFollower', ['user' => $user])->setFrom([\Yii::$app->params['supportEmail'] => \Yii::$app->name])->setTo($user->email)->setSubject('Activity update notification for ' . $project->name . ', acitivity ' . $projectActivity->name)->send();
         }
     }
     $projectFollowerIDs = explode(',', $project->followers->usersFollowing);
     $projectFollowerIDs = array_diff($projectFollowerIDs, $userIds);
     foreach ($projectFollowerIDs as $userId) {
         $user = User::findOne($userId);
         if ($user) {
             \Yii::$app->mailer->compose('emailProjectActivityFollower', ['user' => $user])->setFrom([\Yii::$app->params['supportEmail'] => \Yii::$app->name])->setTo($user->email)->setSubject('Project activity update notification for ' . $project->name)->send();
         }
     }
 }