Learning PHP 5

Chapter 1. Orientation and First Steps

There are lots of great reasons to write computer programs in PHP. Maybe you want to learn PHP because you need to put together a small web site for yourself that has some interactive elements. Perhaps PHP is being used where you work and you have to get up to speed. This chapter provides context for how PHP fits into the puzzle of web site construction: what it can do and why it’s so good at what it does. You’ll also get your first look at the PHP language and see it in action.

PHP’s Place in the Web World

PHP is a programming language that’s used mostly for building web sites. Instead of a PHP program running on a desktop computer for the use of one person, it typically runs on a web server and is accessed by lots of people using web browsers on their own computers. This section explains how PHP fits into the interaction between a web browser and a web server.

When you sit down at your computer and pull up a web page using a browser such as Internet Explorer or Mozilla, you cause a little conversation to happen over the Internet between your computer and another computer. This conversation and how it makes a web page appear on your screen is illustrated in Figure 1-1.

Figure 1-1. Client and server communication without PHP

Here’s what’s happening in the numbered steps of the diagram:

1. You type www.example.com/catalog.html into the location bar ...