Web Database Applications With Php And Mysql (2nd Edition) [Electronic resources] نسخه متنی

Chapter 10. Sessions

A
fundamental characteristic of the Web is the stateless interaction
between browsers and web servers. As discussed in Chapter 1, HTTP is a stateless protocol. Each HTTP
request sent to a web server is independent of any other request. The
stateless nature of HTTP allows users to browse the Web by following
hypertext links and visiting pages in any order. HTTP also allows
applications to distribute or even replicate content across multiple
servers to balance the load generated by a high number of requests.

This stateless nature suits applications that allow users to browse
or search collections of documents. However, applications that
require complex user interaction can't be
implemented as a series of unrelated, stateless web pages. An
often-cited example is a shopping cart in which items are added to
the cart while searching or browsing an on-line store. The state of
the shopping cart (the selected items) needs to be stored somewhere
to be displayed when the user visits the order page.

Stateful web database applications can be built using
sessions, and session management is the topic of
this chapter. In this chapter, we:

Discuss how sessions are managed in the stateless environment of the
Web and introduce the three characteristics of server-side session
management

Show you how to use the PHP session management library, and discuss
design strategies for session-based applications

Use PHP session management to improve the phonebook entry form

Provide a brief list of reasons for using, or avoiding, session
management over the Web

Provide details of the PHP session management API and configuration

There are two ways to build an application that keeps state:
variables that hold the state can be stored in the browser and
included with each request, or variables can be stored on the server.
The focus of this chapter is storing variables on the server using
PHP session management techniques. Storing variables on the client is
usually a less attractive option: it requires additional network
traffic, is insecure, and relies on the user's
browser configuration.