How to create alert notification in Cakephp 3

I’m using this plugin Full Calender to create some Event

now I want to add alert notification when a user create event just like in Social Media I’m not sure if I have to use the Shell for that

I’ve created it in my view

<li role="presentation" class="dropdown">
              <a href="javascript:;" class="dropdown-toggle info-number" data-toggle="dropdown" aria-expanded="false">
                <i class="fa fa-envelope-o"></i>
                <span class="badge bg-green">6</span>
              <ul id="menu1" class="dropdown-menu list-unstyled msg_list" role="menu">

Now I just need in action Controll for it how do I do that please ?
Or does anyone knows another plugin for it

I think you could use Websockets for this.
The CakePHP YouTube channel has a nice talk about this using Ratchet (sidenote: Websockets in PHP can be a hassle at times).

Alternatively, you could use (long)polling with a REST api, but this can (read: most likely will) consume a lot of resources.