PHP is a server-side scripting language

PHP is a server-side scripting language. You can think of it as a "plug-in" for your

Web server that will allow it to do more than just send plain Web pages when

browsers request them. With PHP installed, your Web server will be able to read

a new kind of file (called a PHP script) that can do things like retrieve up-tothe-

minute information from a database and insert it into a Web page before

sending it to the browser that requested it. PHP is completely free to download

and use.

To retrieve information from a database, you first need to have a database. That's

where MySQL comes in. MySQL is a relational database management system,

or RDBMS. Exactly what role it plays and how it works we'll get into later, but

basically it's a software package that is very good at the organization and management

of large amounts of information. MySQL also makes that information really

easy to access with server-side scripting languages like PHP. MySQL is released

under the GNU General Public License (GPL), and is thus free for most uses on

all of the platforms it supports. This includes most Unix-based platforms, like

Linux and even Mac OS X, as well as Windows.

If you're lucky, your current Web host may already have installed MySQL and

PHP on your Web server for you. If that's the case, much of this chapter will not

apply to you, and you can skip straight to the section called “If Your Web Host

Provides PHP and MySQL” to make sure your setup is ship shape.

Everything we'll discuss in this book may be done on a Windows- or Unix-based1

server. The installation procedure will differ in accordance with the type of server

you have at your disposal. The next few sections deal with installation on a

Windows-based Web server, installation under Linux, and installation on Mac

OS X. Unless you're especially curious, you need only read the section that applies

to you.