PHP6 and MySQL® 6 Bible

Chapter 5. Learning PHP Control Structures and Functions

IN THIS CHAPTER

Boolean expressions

Branching

Looping

Terminating execution

Exceptions

Using functions

Function documentation

Defining your own functions

Functions and variable scope

Function scope

It's difficult to write interesting programs if you can't make the course of program execution depend on anything. In a weak sense, the behavior of code that prints variables depends on the variable values, but that is as exciting as filling out a template. As programmers, we want programs that react to something (the world, the time of day, user input, or the contents of a database) by doing something different.

This kind of program reaction requires a control structure, which indicates how different situations should lead to the execution of different code. In Chapter 4, we informally used the if control structure without really explaining it; in this chapter, we lay out every kind of control structure offered by PHP and study their workings in detail.

Note

Experienced C programmers: Of all the features in PHP, control is probably the most reliably C-like — all the structures you are used to are here, and they work the same way.

The two broad types of control structures we will talk about are branches and loops. A branch is a fork in the road for a program's execution — depending on some test or other, the program goes either left or right, possibly following a different path for the rest of the program's execution. A loop is a special kind ...