What Is a Cookie?

This section describes what is a cookie - a piece of information sent by a Web server to a browser. The server expects the browser to send all cookies back to the server.

What Is a Cookie? A cookie is a piece of information sent by a Web server to a Web browser, saved by the browser, and sent back to the server later. Cookies are transmitted inside the HTTP header.

Cookies move from server to browser and back to server as shown in the following diagram:

Web         Web         Local       Web           Web
Server      Browser     System      Browser       Server

Send        Receive     Save        Send back     Receive
cookies --> cookies --> cookies --> cookies   --> cookies

As you can see from the diagram, cookies are actually saved by the local system in memory or on the hard disk of Web browser user's machines. Many users are concerned about this. But I think it is pretty safe to allow your browser to save cookies.

If you are really concerned, you can change your browser's settings to reject cookies. But this may cause many Web based applications fail to run on your browser.

Cookies are mainly used to pass information from one PHP script to the next script.

Last update: 2015.

Table of Contents

 About This Book

 Introduction and Installation of PHP 7.0

 PHP Script File Syntax

 PHP Data Types and Data Literals

 Variables, References, and Constants

 Expressions, Operations and Type Conversions

 Conditional Statements - "if" and "switch"

 Loop Statements - "while", "for", and "do ... while"

 Function Declaration, Arguments, and Return Values

 Arrays - Ordered Maps

 Configuring and Sending out Emails

 Retrieving Information from HTTP Requests

 Creating and Managing Sessions in PHP Scripts

Sending and Receiving Cookies in PHP Scripts

What Is a Cookie?

 Sending and Receiving Cookies

 Sending and Receiving Cookies - Example

 ob_start() - Output Buffering Function

 Persistent Cookies Saved on Hard Disk

 Other Cookie Properties - Domain and Path

 Controlling HTTP Response Header Lines in PHP Scripts

 MySQL Server Connection and Access Functions

 Functions to Manage Directories, Files and Images

 SOAP Extension Function and Calling Web Services

 SOAP Server Functions and Examples

 Localization Overview of Web Applications

 Using Non-ASCII Characters in HTML Documents

 Using Non-ASCII Characters as PHP Script String Literals

 Receiving Non-ASCII Characters from Input Forms

 "mbstring" Extension and Non-ASCII Encoding Management

 Managing Non-ASCII Character Strings with MySQL Servers

 Introduction of Class and Object

 Integrating PHP with Apache Web Server

 Outdated Tutorials

 References

 PDF Printing Version