[`setcookie()`](https://www.php.net/setcookie) has the following signature:

    setcookie ( $name, $value = "", $expires = 0, $path = "", $domain = "", $secure = FALSE, $httponly = FALSE )

You're setting the cookie's value to `1` in your code. I suspect you intend to do something more like

    setcookie('language', $_GET['language'], time() + 1209600, "/", "example.com", false);

## Notes

* This answer doesn't address the security issues in trusting that the `$_GET` data is clean. You should research [data sanitization](https://developer.wordpress.org/themes/theme-security/data-sanitization-escaping/).
* WordPress provides a bunch of handy constants to make something like `time() + 1209600` easier to read. You can do something like `time() + ( 2 * WEEK_IN_SECONDS )`, for example.