Bài giảng Phát triển ứng dụng Web (GV Nguyễn Hữu Thể) Bài 5

PHÁT TRIỂN ỨNG DỤNG WEB

OBJECT ORIENTED PROGRAMMING

Nguyễn Hữu Thể


Content
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.

Class
Visibility
Properties & Methods
Getter & Setter
Create objects
Constructor
Destructor
Inheritance

Abstract class
Interfaces
Autoloading classes
Anonymous functions
Closures
Namespace
2


Class

class ClassName
{
// Properties
// Methods
}

3


Visibility (public, private, protected)
− Three levels:
• public
• private
• protected

− By default, all class members are public.

4

Properties & Methods
class Person
{
private $name; //public, protected
private $age;
public function show(){
echo $this->name . " is " . $this->age . " years old!";

}

}

5


Create objects
(Create a new instance of the class)

− Using the new keyword:
new ClassName()
− For example:
$person = new PerSon();
$person2 = new PerSon();

6


Getter & Setter
PHP

JAVA

class Person
{
private $name;
private $age;

class Person
{
private String name;
private int age;
public String getName(){
return name;
}
public void setName(String name){
this.name = name;
}
public int getAge(){
return age;
}
public void setAge(int age){
this.age = age;
}

public function getName(){
return $this->name;
}
public function setName($name){
$this->name = $name;

}
public function getAge(){
return $this->age;
}
public function setAge($age){
$this->age = $age;
}
}

}

7


class Person{
private $name;
private $age;

Ex: Person.php

public function getName(){
return $this->name;
}
public function setName($name){
$this->name = $name;
}
public function getAge(){
return $this->age;
}
public function setAge($age){

$this->age = $age;
}
public function show(){
echo $this->name . " is " . $this->age . " years old!";
}
}

$p = new Person();
$p->setName("Nguyễn Văn A");
$p->setAge(18);
echo $p->getName() . " is " . $p->getAge() . " years old.";
//echo "{$p->getName()} is {$p->getAge()} years old.";
$p->show();

8


__set() method
class SetName {
public function __set($variable, $value) {
// echo $variable;
echo "My " . $variable . " is " . $value . "\n";
}
}

$obj = new SetName ();
$obj->Name = ‘Tom';
$obj->Name = ‘Jerry';
My Name is Tom
My Name is Jerry

9


__get() method
class GetName {
public $type = 'chocolate';
public $choctype = array (
'milk' => 0,
'dark' => 1,
'plain' => 2
);
public function wrap() {
echo 'Its a wrap';
}
public function __get($index) {
echo '$choctype property with index of: ' . $index . '
';
return $this->choctype [$index];
}
}
$candy = new GetName ();
// set a non existant property

echo 'Value of property is: ' . $candy->milk;

$choctype property with index of: milk
10
Value of property is: 0

Constructor
public function __construct() {
//...
}

public function __construct($name, $age) {
//...
}

11


Constructor
class Person{
private $name;
private $age;
public function __construct($name, $age) {
$this->name = $name;
$this->age = $age;
}
public function show(){
echo $this->name . " is " . $this->age . " years old!";
}

}
$p = new Person("Nguyễn Trần Lê", 18);
$p->show();

12

Destructor
public function __destruct() {
//...
}

− Example:
public function __destruct() {
echo "Bye bye!";
//...
}

− Using:
$p = new Person("Nguyễn Trần Lê", 18);
unset( $p ); // or exit: call __destruct() object
$p->show(); // Object not found
13


Inheritance
class ParentClass {
public function myMethod() {
// Method code here
}
}
class ChildClass extends ParentClass {
public function myMethod() {
// For ChildClass objects, this method is called
// instead of the parent class's MyMethod()

}
}
14


Calling a parent method from a child method
parent::myMethod();

Example:
parent::show();
parent::__construct();

15


require_once 'Person.php';
class Employee extends Person{
private $salary;

}

Inheritance

public function __construct($name, $age, $salary){
parent::__construct($name, $age); // Call __construct() parent
$this->salary = $salary;
}
public function getSalary(){
return $this-> $salary;
}

// Override
public function show(){
parent::show();
echo " Salary: " . $this->salary;
}
public function display(){
echo " Name: " . $this->getName() . "
";
echo " Age: " . $this->getAge() . "
";
echo "Salary: " . $this->salary;
$e = new Employee("Nguyễn Lê", 20, 200);
}
$e->show();
Nguyễn Lê is 20 years old! Salary: 200

16


Visibility (Example 1)
Property Visibility
class MyClass {
public $public = 'Public';
protected $protected = 'Protected';
private $private = 'Private';
function printHello() {
echo $this->public;
echo $this->protected;
echo $this->private;
}
}
$obj = new MyClass();

echo $obj->public; // Works
echo $obj->protected; // Fatal Error
echo $obj->private; // Fatal Error
$obj->printHello(); // Shows Public, Protected and Private
17


Visibility (Example 2)
Property Visibility
class MyClass2 extends MyClass {
// We can redeclare the public and protected method, but not private
public $public = 'Public2';
protected $protected = 'Protected2';
function printHello() {
echo $this->public;
echo $this->protected;
echo $this->private;
}
}
$obj2 = new MyClass2();
echo $obj2->public; // Works
echo $obj2->protected; // Fatal Error
echo $obj2->private; // Undefined
$obj2->printHello(); // Shows Public2, Protected2, Undefined
18


Visibility (Example 3)
Method Visibility
class MyClass {

// Declare a public constructor
public function __construct() { }
// Declare a public method
public function MyPublic() { }

// Declare a protected method
protected function MyProtected() { }
// Declare a private method
private function MyPrivate() { }

// This is public
function Foo() {
$this->MyPublic();
$this->MyProtected();
$this->MyPrivate();
}
}

$myclass = new MyClass;
$myclass->MyPublic(); // Works
$myclass->MyProtected(); // Fatal Error
$myclass->MyPrivate(); // Fatal Error
$myclass->Foo(); // Public, Protected and Private work

19


Visibility (Example 4)
Method Visibility
class MyClass2 extends MyClass

{
// This is public
function Foo2()
{
$this->MyPublic();
$this->MyProtected();
$this->MyPrivate(); // Fatal Error
}
}
$myclass2 = new MyClass2;
$myclass2->MyPublic(); // Works
$myclass2->Foo2(); // Public and Protected work, not Private
20


Visibility (Example 5)
Method Visibility
class Bar
{
public function test() {
$this->testPrivate();
$this->testPublic();
}

class Foo extends Bar
{
public function testPublic() {
echo "Foo::testPublic\n";
}
private function testPrivate() {

echo "Foo::testPrivate\n";
}

public function testPublic() {
echo "Bar::testPublic\n";
}

}

private function testPrivate() {
echo "Bar::testPrivate\n";
}

$myFoo = new Foo();
$myFoo->test(); // Bar::testPrivate
// Foo::testPublic

}
21


Abstract class
− An abstract class is a class that cannot be instantiated on its
own.
abstract class Mathematics{
/*** child class must define these methods ***/
abstract protected function getMessage();
abstract protected function add($num);
/**
* method common to both classes

**/
public function showMessage() {
echo $this->getMessage();
}
}
22


Abstract class
require_once 'Mathematics.php';
class myMath extends Mathematics {
protected function getMessage() {
return "The anwser is: ";
}
public function add($num) {
return $num + 2;
}
}
// A new instance of myMath
$myMath = new MyMath ();
$myMath->showMessage ();
echo $myMath->add (4);
The anwser is: 6
23


Interfaces
− An interface declares one or more methods.
− Must be implemented by any class that implements the
interface.

interface MyInterface {
public function aMethod();
public function anotherMethod();
}
class MyClass implements MyInterface {
public function aMethod() {
// (code to implement the method)
}
public function anotherMethod() {
// (code to implement the method)
}
}
24


interface Persistable {
public function save();
public function load();
public function delete();
}
require_once 'Persistable.php';
class Member implements Persistable {
private $username;
private $location;
private $homepage;
public function __construct( $username,
$location, $homepage ) {
$this->username = $username;
$this->location = $location;
$this->homepage = $homepage;

}
public function getUsername() {
return $this->username;
}
public function getLocation() {
return $this->location;
}
public function getHomepage() {
return $this->homepage;
}

public function save() {
echo "Saving member to
database
";
}
public function load() {
echo "Loading member from
database
";
}
public function delete () {
echo "Deleting member from
database
";
}
}
$m = new Member("Aha", "VN", "No page");
echo $m->getUsername() . "
";
$m->load();
//...
Aha
Loading member from database