Cookies and Session Management

Using regular HTML pages, when a browser requests a page from a server, the server will serve that page to the client then simply forgets about it! No knowledge of the client is kept between requests. Certainly the client browser will keep a record of the pages in the History object, but unless we do something no other information is kept. In a suite of web pages this means that if we enter information in one form, it will not automatically be available to other pages in the web application.

HTML and PHP offer various methods to make a web viewing session "stateful":

Query Strings: Information can also be kept in the query string. The draw back of this of course is that the information is visible.
Hidden Input elements: Information can be passed from page to page using hidden form elements.
Cookies: Cookies are strings that are stored on the clients computer which are Domain specific.
Sessions: PHP includes a sessions management system that allows to treat any single session on a single client as a unified whole.
Frames: All the variables would be placed in one of the Frames using JavaScript. These would then be available in any of the other frames. This method is really only of Historical interest.