Using cookie to track users

there are two ways to track someone while they are going to page to page. You can write some kind of ID to their cookie, and then retrieve that ID on the next page load. You can then use that ID to retrieve and write information to a database table such as what page they just went to. This does rely on cookies working on the visitors web browser. You can write / read the ID directly to / from the cookie, but using codeigniter 'sessions' gives you much more functionality. any information written to a cookie is unique to the visitor, but its not private - its part of the http headers that are sent by the browser.

The other way to track page to page is to create an ID, but instead of writing it to the cookie, you pass it in a hidden form field or added to the URL string. then when the person goes to the next page, you get the ID, retrieve and write the info, etc etc.