Beginning PHP 5.3

Chapter 3. PHP Language Basics

So far you've looked at what PHP is, and what you can use it for. You've also written and tested a simple PHP script to give you a feel for how the language works. Now, in these next few chapters, you'll build a solid foundation of knowledge that you can use to create more complex applications and Web sites in PHP.

This chapter gets the ball rolling. In it you explore some of the fundamental concepts of PHP — its building blocks, if you will. You learn about:

• Variables, which let you store and manipulate data in your scripts

• Data types, including which types are available in PHP, and how to test for and change type

• PHP's available operators, which you can use to manipulate information

• Constants, which are useful for storing data that doesn't change in your script

These are all important concepts, both in PHP and in other programming languages. Once you've read and digested this chapter, you'll be ready to move on and tackle the other features of the PHP language.

Using Variables in PHP

Variables are a fundamental part of any programming language. A variable is simply a container that holds a certain value. Variables get their name because that certain value can change throughout the execution of the script. It's this ability to contain changing values that make variables so useful.

For example, consider the following simple PHP script:

echo 2 + 2;

As you might imagine, this code outputs the number 4 when it's run. This is all well and good; however, if you wanted ...