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setting js cookie then accessing with php in same page – undefined till page is refreshed

Is it possible to set this cookie with js then access it later in the body with php? No matter where I put my script when I echo with php it is always undefined until I refresh the page. I can put it in the head, above html, etc… doesn’t matter. What I want to be able to achieve is having that cookie set for use in my page – with php – without the refresh needed. Example case would be the initial page visit from a user on my site. The session.php is what starts the session.

test.php :

<?php
require $_SERVER['DOCUMENT_ROOT'].'/assets/functions/session.php';
?>

<!DOCTYPE html>
<html class="no-js" lang="en">

<!-- BEGIN HEAD -->
<head>
    <script>
            //returns browser timezone or defaults to UTC
            var tz = Intl.DateTimeFormat().resolvedOptions().timeZone ?? 'UTC';

            //store as cookie so you can use it with php
            //document.cookie = "test_Timezone="+tz+"; expires=0; path=/; domain=test.com; secure; samesite=lax";
            document.cookie = "test_Timezone="+tz+"; expires=0; path=/; domain=test.bs5; samesite=lax";

    </script>
</head>
<!-- END HEAD -->

<!-- BEGIN BODY -->
<body>

    <?php
        echo 'timezone is : '.$_COOKIE['test_Timezone'];
    ?>
</body>
<!-- END BODY -->
</html>
Tags:

2

Answers


  1. 0

    Server side code (PHP in your case) is executed before the client side script is executed; so you are attempting to retrieve cookie information that has not yet been stored.

    You could either:

    1. Use PHP to set the cookie, you will no longer rely on JS to do so so you can get the contents in the same script
    2. Create a "bounce" page, a redirect, where you set the cookie in JS (if you must) and redirect to the PHP script which would get the cookie’s contents set from the redirect
    3. You can make an AJAX call to set the cookie within your page to set the cookie in a separate script, and on success of that call you’d set your getters

    These are some creative ways that could resolve your issue.

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  2. 0

    The reason for this is that you have two actors here: the server and the client. It may happen to be the same machine while you work as a developer, but later on they may be two distinct, remote machines.

    The flow is:

    • the client sends a request to the server
    • the server acknowledges the client’s request
    • so it will run your PHP
    • and generate the HTML
    • and proceeds sending your HTML to the client
    • the client receives the HTML, parses it
    • and then it displays it as well as executing your programmatic code

    So your server will already have executed your PHP by the time your client is to execute your Javascript, independently of where you put your script textually. If you need to save a cookie and proceed with using it inside PHP, then you will need to send a request to your server. For this purpose you could test for isset($_COOKIE['test_Timezone']) and if it happens to be true, then display it. If it’s not true, then reload the page.

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