Cookies are a way for a server to store information on the user’s machine. This is one way that a site can remember or track a user over the course of a visit. Think of a cookie like a name tag: you tell the server your name and it gives you a sticker to wear. Then it can know who you are by referring back to that name tag.
Testing for Cookies
To effectively program using cookies, you need to be able to accurately test for their presence. The best way to do so is to have your Web browser ask what to do when receiving a cookie. In such a case, the browser will prompt you with the cookie information each time PHP attempts to send a cookie.
Different versions of different browsers on different platforms all define their cookie handling ...