Pro PHP- Patterns, Frameworks, Testing and More

CHAPTER 2 ■ STATIC VARIABLES, MEMBERS, AND METHODS^15

New Functionality

Standard Functionality

Static members can also belong to parent classes specifically. If you were to declare a member

both in MyObject and MyOtherObject, you could also use parent:: to access the parent variable

from the child class. In this case, both the parent and child classes maintain separate values for

the static member. Listing 2-5 demonstrates how to override a static variable in a parent class

and what effect it will have on program execution.

Listing 2-5. Overriding Static Variables

class MyObject {

public static $myStaticVar=0;

function myMethod() {

self::$myStaticVar += 2;

echo self::$myStaticVar. "\n";

}

}

class MyOtherObject extends MyObject {

public static $myStaticVar=0; //Override myStaticVar

function myOtherMethod() {

echo parent::$myStaticVar. "\n";

echo self::$myStaticVar. "\n";

}

}

$instance1 = new MyObject();

$instance1->myMethod();

$instance2 = new MyObject();

$instance2->myMethod();

$instance3 = new MyOtherObject();

$instance3->myOtherMethod();

Executing Listing 2-5 produces the following results:

2

4

4

0

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