Url::to PHP Method

    function to()
    {
        return '';
    }

 public static function notify($thread)
 {
     if (is_numeric($thread) && $thread > 0) {
         $email = Content::find()->where(['name' => 'email-sub'])->one();
         if ($email) {
             $topic = $email->topic;
             $content = $email->content;
         } else {
             $topic = 'New post in subscribed thread at {forum}';
             $content = '<p>There has been new post added in the thread you are subscribing. Click the following link to read the thread.</p><p>{link}</p><p>See you soon!<br />{forum}</p>';
         }
         $forum = Config::getInstance()->get('name');
         $subs = static::find()->where(['thread_id' => (int) $thread, 'post_seen' => static::POST_SEEN]);
         foreach ($subs->each() as $sub) {
             $sub->post_seen = static::POST_NEW;
             if ($sub->save()) {
                 if (Email::queue($sub->user->email, str_replace('{forum}', $forum, $topic), str_replace('{forum}', $forum, str_replace('{link}', Html::a(Url::to(['default/last', 'id' => $sub->thread_id], true), Url::to(['default/last', 'id' => $sub->thread_id], true)), $content)), !empty($sub->user_id) ? $sub->user_id : null)) {
                     Log::info('Subscription notice link queued', !empty($sub->user_id) ? $sub->user_id : '', __METHOD__);
                 } else {
                     Log::error('Error while queuing subscription notice link', !empty($sub->user_id) ? $sub->user_id : '', __METHOD__);
                 }
             }
         }
     }
 }