When a user first encounters a page in your application that call ssession start(),a sessionis created for the user.PHP generates a random session identifier to identify the user,and then it sends a set-Cookieheader to the client.By default,the name of this cookie is PHPSESSID,but it is possible to change the cookiename in php.ini or by using the session name() function.On subsequent visits,the client identifies the user with the cookie,and this is how thea application maintains state.