OOP in PHP

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Information about OOP in PHP
Education

Published on February 10, 2014

Author: sicarii_13

Source: slideshare.net

Description

Object orientation is probably the area that has been subject to the most significant and far-reaching changes with the advent of PHP 5. Rather than making things incompatible with previous versions of the language, however, they enhance PHP 4’s meagre OOP offerings and make PHP 5 a fully functional object-oriented language.

FUNDAMENTALS •Classes •Encapsulation •Objects

CLASS DECLARATION The basic declaration of a class is very simple: class myClass { // Class contents go here }

OBJECT INSTANTIATION This is done by using the new construct: $myClassInstance = new myClass(); An object is always passed by reference rather than by value. $myClassInstance = new myClass(); $copyInstance = $myClassInstance();

CLASS INHERITANCE Allows a class to extend another class, essentially adding new methods and properties, as well as overriding existing ones as needed. class a { function test() { echo "a::test called"; } function func() { echo "a::func called"; } } class b extends a { function test() { echo "b::test called"; } } class c extends b { function test() { parent::test(); } } class d extends c { function test() { b::test(); } } $a = new a(); $b = new b(); $c = new c(); $d = new d();

METHODS AND PROPERTIES Methods are declared just like traditional functions: class myClass { function myFunction() { echo "You called myClass::myFunction"; } } From outside the scope of a class, its methods are called using the indirection operator ->: $obj = new myClass(); $obj->myFunction();

METHODS AND PROPERTIES class myClass { function myFunction($data) { echo "The value is $data"; } function callMyFunction($data) { // Call myFunction() $this->myFunction($data); } } $obj = new myClass(); $obj->callMyFunction(123);

CONSTRUCTORS class foo { function __construct() { echo __METHOD__; } function foo() { // PHP 4 style constructor } } new foo();

DESTRUCTORS class foo { function __construct() { echo __METHOD__ . PHP_EOL; } function __destruct() { echo __METHOD__; } } new foo(); This code will display: foo::__construct foo::__destruct

VISIBILITY public The resource can be accessed from any scope. protected The resource can only be accessed from within the class where it is defined and its descendants. private The resource can only be accessed from within the class where it is defined. The resource is accessible from any scope, but cannot be overridden in descendant classes. final

DECLARING AND ACCESSING PROPERTIES class foo { public $bar; protected $baz; private $bas; public $var1 = "Test"; // String public $var2 = 1.23; // Numeric value public $var3 = array (1, 2, 3); }

CONSTANTS, STATIC METHODS AND PROPERTIES class foo { static $bar = "bat"; public static function baz() { echo "Hello World"; } } $foo = new foo(); $foo->baz(); echo $foo->bar; Hello WorldPHP Strict Standards: Accessing static property foo::$bar as non static in PHPDocument1 on line 17 Strict Standards: Accessing static property foo::$bar as non static in PHPDocument1 on line 1

CLASS CONSTANTS class foo { const BAR = "Hello World"; } echo foo::BAR;

INTERFACES AND ABSTRACT CLASSES •An abstract class essentially defines the basic skeleton of a specific type of encapsulated entity. •Interfaces, on the other hand, are used to specify an API that a class must implement.

EXCEPTIONS • Exceptions provide an error control mechanism that is more fine-grained than traditional PHP fault handling, and that allows for a much greater degree of control. • Key differences between “regular” PHP errors and exceptions: • Exceptions are objects, created (or “thrown”) when an error occurs • Exceptions can be handled at different points in a script’s execution, and different types of exceptions can be handled by separate portions of a script’s code • All unhandled exceptions are fatal • Exceptions can be thrown from the __construct method on failure • Exceptions change the flow of the application

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