Can I Set a Cookie for a Different Domain?

Navigating Cross-Domain Cookie Conundrum

Problem:
In the realm of website development, it may arise that you wish to set a cookie for a different domain than the one currently being accessed. For instance, you have a website at a.com and aim to set a cookie for b.com when a specific page, a.com/link, is loaded. Following that, you plan to redirect the user to b.com.

Is Cross-Domain Cookie Setting Possible?

The simple answer is: no, it is not possible to directly set cookies for other domains. This limitation stems from the fundamental security implications it could pose.

Workaround for Cross-Domain Cookie Setting

To overcome this hurdle, you must rely upon the assistance of b.com. To set the cookie for b.com, you must redirect the user to a specific URL on b.com that includes the instructions to set the cookie. For example:

a.com/link -> b.com/setcookie.php?c=value

The setcookie script at b.com/setcookie.php could perform the necessary cookie setting and then redirect the user to the desired page on b.com, as illustrated below:

<?php
    setcookie('a', $_GET['c']);
    header("Location: b.com/landingpage.php");
?>

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