push notifications not appearing as popups at the bottom right corner of the screen for web app

I am working on push notifications by using Google's firebase for a web app(desktop). I have implemented the code given by Google to generate a token on the client's computer by using my credentials of firebase.

The issue is that when I send the request by using ARC client of chrome, I receive the notification popup. But when I try to send the request by using CURL in PHP, I get a success message and the messaged gets displayed on my localhost/index.html (used to generate token and to manage push notification [provided by Google firebase]). Here is the message that gets displayed.

Received message:

{
  "from": "565634123456",
  "collapse_key": "do_not_collapse",
  "notification": {
    "title": "Test title",
    "body": "Test content",
    "icon": "firebase-logo.png",
    "click_action": "http://localhost/index.html"
  }
}

I wanted a notification popup to appear and not the successful message to be displayed on my index.html. Can anyone please guide here?