How can the same origin policy affect the ability to set cookies across different subdomains in PHP?

The same origin policy restricts the ability to set cookies across different subdomains in PHP. To overcome this limitation, you can set the domain parameter of the cookie to the root domain shared by all subdomains. This allows the cookie to be accessed by all subdomains within that root domain.

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