MySQL Cookbook, 2nd Edition

Introduction

Many web applications interact with users over a series of requests and, as a result, need to remember information from one request to the next. A set of related requests is called a session. Sessions are useful for activities such as performing login operations and associating a logged-in user with subsequent requests, managing a multiple-stage online ordering process, gathering input from a user in stages (possibly tailoring the questions asked to the user’s earlier responses), and remembering user preferences from visit to visit. Unfortunately, HTTP is a stateless protocol, which means that web servers treat each request independently of any other—unless you take steps to ensure otherwise.

This chapter shows how to make information persist across multiple requests, which will help you develop applications for which one request retains memory of previous ones. The techniques shown here are general enough that you should be able to adapt them to a variety of state-maintaining web applications.

Session Management Issues

Some session management methods rely on information stored on the client. One way to implement client-side storage is to use cookies, which are implemented as information that is transmitted back and forth in special request and response headers. When a session begins, the application generates and sends the client a cookie containing the initial information to be stored. The client returns the cookie to the server with each subsequent request to identify ...