PHP application for medium interface such as Object-oriented development (interface, implements) _php tutorial

The application key of the interface in PHP class is interface, implements, interface is a kind of special abstract class that member property is all abstract or constant, below we see several examples.

Application of interfaces in class

1. Keywords: interface
2. Keywords: implements

1. Introduction and creation of the interface

Interface: A special abstract class in which member properties are all abstract or constant.

Rules:

1. All of the classes are abstract methods.
2. Abstract method Money is not added to abstract.
3. The interface abstract method property is public.
4. The member property must be a constant.

Format:

The code is as follows	Copy Code
Interface Demo { Const NAME = "Constant object property"; function fun1 (); function fun2 (); Abstract method. }

2. Application and specification of interface

Interface references differ from class-inheriting keyword extends, where inheritance can only be singular, and interfaces may use keywords to implements multiple references and separate them with commas

1. Format: normal class reference interface

Class MyPc implements demo, Demo2, Demo3 {
...
}

2. Format: Abstract class Application Interface example

Abstract class MyPc implements demo, Demo2, Demo3 {
...
}

3. Format: Inherit parent class reference interface coexist

Class MyPc extends Root implements demo, Demo2, Demo3 {
...
}

Inherit the Post interface first, and then inherit the multiple interfaces.

4. Format: interface and interface inheritance

Interface Demo3 extends Demo {
...
}

Instance:

The code is as follows

Copy Code

Interface Demo { Const NAME = "Name"; function fun1 (); function fun2 (); } Interface Demo2 { function Fun3 (); function Fun4 (); } Interface Demo3 { Const TEST = "Test"; function Fun5 (); } Class MyPc implements demo, Demo2 { function Fun1 () { echo "++++++++++ "; } function fun2 () { echo "---------- "; } function Fun3 () { echo "1111111111 "; } function Fun4 () { echo "2222222222 "; } } Class Myps extends MyPc implements DEMO3 { function Fun5 () { echo "Inherit class after reference interface"; } } $p = new Myps; $p->fun1 (); $p->fun2 (); $p->fun3 (); $p->fun4 (); $p->fun5 (); ?>

Cases

The interface is defined using the keyword interface, and the method in the interface is implemented using the keyword implements, and must be fully implemented.

Example:

The code is as follows

Copy Code

Defining interfaces Interface user{ function Getdiscount (); function Getusertype (); } VIP User Interface Implementation Class Vipuser implements user{ VIP User Discount Factor Private $discount = 0.8; function Getdiscount () { return $this->discount; } function Getusertype () { Return "VIP user"; } } Class goods{ var $price = 100; var $vc; Defines the user interface type parameter, at which point it is not known what users function run (User $VC) { $this->VC = $VC; $discount = $this->vc->getdiscount (); $usertype = $this->vc->getusertype (); echo $usertype. " Commodity price: ". $this->price* $discount; } } $display = new Goods (); $display->run (new Vipuser); Can be more other user types ?>

To run the example, output:

VIP User Commodity price: 80 yuan

This example demonstrates a simple application of a PHP interface. In this example, the user interface implements a discount for users, and a specific discount factor is implemented within the Vipuser class. Finally, the product class Goods according to the user interface to achieve different customer quotes.

This example is limited to demonstrating the usage of the PHP interface and does not involve its science or not.

Implementing multiple interfaces

PHP can also implement multiple interfaces at the same time as inheriting a class:

Class Subclass extends Parent class Implemtns interface 1, interface 2, ...
{
......
}

The difference between an abstract class and an interface

An interface is a special abstract class and can also be seen as a specification of a model. Interfaces are roughly different from abstract classes:

1. A subclass if you implements an interface, you must implement all the methods in the interface (whether or not it is required), or if you are inheriting an abstract class, you only need to implement the required method.
2. If the method name defined in one of the interfaces changes, then all subclasses implementing this interface need to update the method name synchronously, whereas in an abstract class if the method name changes, the corresponding method names of its subclasses are not affected, but only become a new method (relatively old method implementation).
3. Abstract classes can only be inherited, and when a subclass needs to implement functionality that needs to inherit from more than one parent class, the interface must be used.

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