We've looked at what PHP is, and how to install and configure it, so now it's time to look at the basic constructs which make up the PHP programming language. While PHP syntax draws inspiration from a number of sources, notably C, UNIX shell scripting languages, and Perl, it is very much its own language. The following two chapters, while not intended to be a complete tutorial in PHP syntax, should serve to help someone familiar with other languages, or with basic PHP, to understand the code structures that PHP provides. For a more thorough treatment of the basics of PHP programming, take a look at Beginning PHP4 from Wrox Press.
The first thing we need to understand is how PHP code is structured, in terms of code blocks, statements, comments, and so on. Then we can look at syntax in more detail. The syntax of most structured programming languages can be broken down into three areas: data storage, flow control, and modularization. Data storage is principally provided via variables, and that is what we'll concentrate on in this chapter.
The areas we'll consider in this chapter are:
PHP scripting elements
Literals
Variables
Data types
Expressions and operators
Form variables
System variables