Are there specific coding practices or configurations in PHP that can help ensure cookie functionality across subdomains?

To ensure cookie functionality across subdomains in PHP, you can set the cookie domain parameter to the root domain of your website. This allows the cookie to be accessible across all subdomains. Additionally, you should also set the cookie path parameter to '/' to ensure the cookie is accessible on all paths within the domain.

setcookie('cookie_name', 'cookie_value', time() + 3600, '/', '.yourdomain.com');