How can PHP developers ensure that cookies remain valid and accessible across different domain variations, such as forcing "www." or non-"www." through redirection?

To ensure that cookies remain valid and accessible across different domain variations, such as forcing "www." or non-"www." through redirection, PHP developers can set the cookie domain to the root domain and use a server-side redirection to enforce the desired domain format. 

// Set the cookie domain to the root domain
$domain = ($_SERVER['HTTP_HOST'] != 'localhost') ? $_SERVER['HTTP_HOST'] : false;
setcookie('cookie_name', 'cookie_value', time() + 3600, '/', $domain);

// Redirect to the desired domain format
if (substr($_SERVER['HTTP_HOST'], 0, 4) !== 'www.') {
    header('Location: https://www.' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']);
    exit;
}

Keywords

PHP cookies domain redirection validation

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