PHP Cookies across multiple sub domains

Here's how to make the browser store cookies across multiple sub domains.

The example I have used is for my site. The cookie given to the browser will be used for any *.dtbaker.com.au address. The PHP code creates a new session with a random session id, that session id is stored in the cookie, and the cookie is sent to the browser. Next time the browser sends a requests, it will send the cookie that contains the session id.

Here's the PHP code:

define("SESSION_NAME","S_DTBAKER");
if(!isset($_COOKIE[SESSION_NAME])){
        // new session id
        session_id( md5 ( uniqid ( microtime () ) ) );
        session_name ( SESSION_NAME );
        session_start();
        // send cookie - change dtbaker.com.au to your domain name
        setcookie( SESSION_NAME, session_id(), 0, '/', '.dtbaker.com.au');
}else{
        session_id( $_COOKIE[SESSION_NAME] );
        session_name( SESSION_NAME );
        session_start();
}