How Does PHP Session Work
The Hyper Text Transfer Protocol is a stateless protocol. That means server just forget about you when your request is served and the connection between server and client is immediately closed after that. For example, when you made a request for page a.html, the server send you the a.html. After that, you made second request for b.html. In that time, the server won't recognize that you are the one who previously request a.html.