The right notification for the phone?

Question

Web development

Good afternoon. I am writing an application (chat) in react native. It is necessary to send an alert to the phone and count the number of unread messages. I'm going to remember the number of the last message when a person exits and use the firebase functions to hang a handler that will increase the number of unread messages. and every time when he will increase the number, I want to send messages to the phone. For this I want to use firebase functions.
The question is whether the logic is correct and is there an easier way to solve these problems?

Answer 1

Need to execute the user lookup code before the cookie is declared

Answer 2

Because cookies are http header
Code:

<?php
setcookie('test', 12);
echo $_COOKIE['test'];

Let's run it for the first time:
Let's run it a second time:
12