Detailed explanation of polymorphism in PHP object-oriented development

Detailed explanation of polymorphism in PHP object-oriented development_PHP tutorial

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Release： 2016-07-13 10:50:18

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This article will introduce you to the detailed explanation of polymorphism in PHP object-oriented development. I hope this tutorial will be helpful to you.

Polymorphism of classes

1. Introduction and advantages of polymorphism.
2. Operator: instanceof.
3. Simple application of polymorphism.

1. Introduction and advantages of polymorphism

Introduction: Polymorphism is the third feature of object-oriented languages after abstraction and inheritance.

Example: USB interface, different functions will be used when plugging different things into it.

Advantages: OOP is not just a collection of many functions and functions, the purpose is to use classes, inheritance, and polymorphism to describe a situation in our lives.

2. Operator: instanceof

PHP is a type operator used to determine whether a given object comes from a specified object
Format:

The code is as follows

Copy code

代码如下

复制代码

class A {}
class B {}

$thing = new A;
if ($thing instanceof A) {
echo "A";
}
if ($thing instanceof B) {
echo "B";
}

class A {}

class B {}

$thing = new A;

代码如下

复制代码

class A {

}

class B {

}

$new = new A;

if ($new instanceof A) {
echo "A";
}
if ($new instanceof B) {
echo "B";
}
?>

if ($thing instanceof A) {

echo "A";

}

if ($thing instanceof B) {

代码如下

复制代码

interface MyUsb {
function type();
function alert();
}

class Zip implements MyUsb {
function type() {
echo "2.0";
}
function alert() {
echo "U盘驱动正在检测……
";
}
}

class Mp3 implements MyUsb {
function type() {
echo "1.0";
}
function alert() {
echo "MP3驱动正在检测……";
}
}

class MyPc {
function Add_Usb($what) {
$what->type();
$what->alert();
}

}
$p = new MyPc();

$zip = new Zip();

$mp3 = new Mp3();

$p->Add_Usb($zip);
$p->Add_Usb($mp3);
?>

echo "B"; }

3. Simple application of polymorphism Example 1:

The code is as follows	Copy code
class A {<🎜> <🎜>}<🎜> <🎜>class B {<🎜> <🎜>}<🎜> <🎜>$new = new A;<🎜> <🎜>if ($new instanceof A) {<🎜> echo "A";<🎜> }<🎜> if ($new instanceof B) {<🎜> echo "B";<🎜> }<🎜> ?>

Example 2:

The code is as follows

Copy code

interface MyUsb {<🎜> function type();<🎜> function alert();<🎜> }<🎜> <🎜>class Zip implements MyUsb {<🎜> function type() {<🎜> echo "2.0";<🎜> }<🎜> function alert() {<🎜> echo "The USB drive is detecting...
"; } } class Mp3 implements MyUsb { function type() { echo "1.0"; } function alert() { echo "MP3 driver is detecting..."; } } class MyPc { function Add_Usb($what) { $what->type(); $what->alert(); } } $p = new MyPc(); $zip = new Zip(); $mp3 = new Mp3(); $p->Add_Usb($zip); $p->Add_Usb($mp3); ?>

Added an example 213.29.11.16 update

Inheritance and Polymorphism

/* Parent class */
class MyObject{
public $object_name; //Book name
public $object_price; //Book price
public $object_num; //Number of books
public $object_agio; //Book discount
function __construct($name,$price,$num,$agio){ //Constructor
$this -> object_name = $name;
$this -> object_price = $price;
$this -> object_num = $num;
$this -> object_agio = $agio;
}
function showMe(){ //Output function
The sentence echo ' will not be displayed. ';
}
}
/* Subclass Book */
class Book extends MyObject{ //Subclass of MyObject.
public $book_type; //Category
function __construct($type,$num){ //Declare the constructor method
$this -> book_type = $type;
$this -> object_num = $num;
}
function showMe(){ //Rewrite the showMe method in the parent class
return 'This time'.$this -> book_type.'Book'.$this->object_num.'this
';
}
}
/* Subclass Elec */
class Elec extends MyObject{ //Another subclass of MyObject
function showMe(){ //Rewrite the showMe method in the parent class
return 'Hot-selling books:'.$this -> object_name.'
Original price: '.$this -> object_price.'
Special price: '.$this -> object_price * $this -> ; object_agio;
}
}
/* Instantiate object */
$c_book = new Book('Computer class',1000); //Declare a Book subclass object
$h_elec = new Elec('PHP Function Reference Collection',98,3,0.8); //Declare an Elec subclass object
echo $c_book->showMe()."
"; //Output the showMe() method of Book subclass
echo $h_elec->showMe(); //The showMe() method that outputs the Elec subclass is
?>