Pro PHP- Patterns, Frameworks, Testing and More

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CHAPTER 2

Static Variables, Members,

and Methods

This chapter discusses the static keyword as it is applied to variables, classes, and methods.

You will learn about the scope resolution operator (::) and its implication in object-oriented

design. Finally, I will touch on the often heated debate about the usage of static classes in appli-

cation design.

To get the most from this chapter, you should already be familiar with variable scope; that

is, you should understand global, function, and class scope, and the use of the $this variable

within classes.

Static Variables

A static variable is a variable that exists only in function scope, but that does not lose its value

when the function is finished executing; that is, it remembers its value the next time the function is

called.

To declare a variable as static, you simply prefix the variable with the static keyword, as

shown in Listing 2-1.

Listing 2-1. Declaring a Basic Static Variable

function testing() {

static $a = 1;

$a *= 2;

echo $a. "\n";

}

testing();

testing();

testing();

Executing Listing 2-1 produces the following output:

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