Why is the value not being passed from js to php?

Question

PHP

Welcome all.
Explain why my value and JS are not being passed to PHP and how to do it correctly.

<script>
var abcd = 2222;
</script>

$GetVar = "<script>document.write(abcd)</script>"; 
    console.log($GetVar);

Console is empty. No errors are observed.

Also, the question is of interest: what is the actual way to transfer the value of a variable from PHP to JS?

Answer 1

You generally have a language written in some kind of PHJS.
You can transfer from PHP to JS like this:

<?php

$abcd = 1234;

?>
<script>
    var abcd = <?= json_encode($abcd) ?>;
    var abcd = <?= $abcd ?>;
    console.log(abcd);
</script>

You need to pass a value from JS to PHP via AJAX (go to the search, there are a lot of such questions)

Answer 2

PHP is a server-side language and JS is a client-side language (runs in a browser). First, the PHP script will be executed, and only then the JS script will be executed.
For your task - you need to pass data to a php script, this can be done through a form or an ajax request