Applications of interfaces in php classes--implements

The application keywords of the interface in the php class are interface and implements. The interface is a special abstract class whose member attributes are all abstract or constant. Implements mainly refers to the class name, the methods owned by the class, and the parameters passed It functions as a constraint and specification, a bit like an abstract class.

Application of interface in class

1. Keyword: interface

2. Keyword: implements

1. Introduction and creation of interface

Interface: a special abstract class whose member attributes are all abstract or constant.

Rules:

1. All methods in the class are abstract.

2. There is no need to add abstract for abstract methods.

3. The interface abstract method attribute is public.

4. Member attributes must be constants.

The format code is as follows:

interface demo { 
const NAME = "常量对象属性"; 
function myfun1(); //抽象方法function myfun2(); //抽象方法,不用具体写入逻辑 }

1. Definition and calling of the interface

<?phpinterface Cinema
{const film = &#39;加勒比海盗&#39;;public function show();
}class Order implements Cinema
{public function show()
    {echo "影院 接口开放了<br>";
    }
}$face = new Order();echo $face->show();       
echo Cinema::film;

Instructions : One thing to note in the above example is that the method name of the interface is show, and the class that inherits the interface must have the show method, otherwise an error will be reported. In other words, the methods of the interface are fake, and what really works are the methods in the inherited class. Is the interface here a bit similar to the abstract class of PHP?<br>Second, the parameter constraints are strict

<?phpinterface Cinema
{public function show(Order $show,$num);
}// 显示正常class Order implements Cinema
{public $number=&#39;0011排&#39;;public function show(Order $show,$num)
    {echo $show->number.$num;
    }
}$face= new Order();$face->show(new Order,$num='3人');//输出 0011排3人

Note: The above example inherits the interface class. When calling the interface method, the parameters passed must be consistent with the parameter names in the interface. Otherwise, an error will be reported.

3. Inheritance between interfaces and passing parameters by calling the interface

<?phpinterface Cinema
{public function show();
}interface Cinema1 extends Cinema
{public function show1(Order1 $object,$num);
}class Order implements Cinema1
{public function show()
    {echo "准备就绪<br>";
    }public function show1(Order1 $object,$num)
    {//var_dump($object);echo $object->number."$num<br>";
    }
}class Order1
{public $number="0012排";function fun(){echo ' =================';
    }
}$show = new Order1;$show->fun();          
$test = new Order();$test->show();           
$test->show1($show,$num='6人');// 输出 ===============准备就绪0012排6人

Explanation: You can see the above example , the interface Cinema1 inherits the interface Cinemal, and the class Order inherits the interface Cinema1. I don’t know if you have noticed, but the class Order includes two methods, one is show and the other is show1, and no one is missing. If one is missing, a fatal error will be reported. Order1 in show1(Order1 $object,$num) must have the same name as class Order1. If they are different, a fatal error will be reported. So what should we do if an interface is inherited by multiple classes and the class names are different? Then you have to use self, which will be mentioned below

Four, multiple inheritance for one interface

<br>

<?php
interface demo {
    const NAME = "电影名称";
    function fun1();
    function fun2();
}
interface demo2 {
    function fun3();
    function fun4();
}
interface demo3 {
    const TEST = "这里是测试Test";
    function fun5();
}
class MyDemo implements demo, demo2 {
    function fun1() {
        echo "你好";
    }
    function fun2() {
        echo "----------";
    }
    function fun3() {
        echo "我也好<br />";
    }
    function fun4() {
        echo "大家都好<br />";
    }
}
class YourDemo extends MyDemo implements demo3 {
    function fun5() {
        echo "继承类后引用接口";
    }
}
$p = new YourDemo;
$p->fun1();
$p->fun2();
$p->fun3();
$p->fun4();
$p->fun5();

The above output

你好----------我也好
大家都好
继承类后引用接口

In the above example, we can see that interfaces are defined using the keyword interface, and the keyword implements is used to implement the methods in the interface. Another example:

<?php//定义接口interface User{function getDiscount();function getUserType();
}class VipUser implements User{ //VIP用户 接口实现private $discount = 0.8;    // VIP 用户折扣系数function getDiscount() {return $this->discount;
    }function getUserType() {return "VIP用户";
    }
}class Goods{var $price = 88;var $vc;function run(User $vc){     //定义 User 接口类型参数，这时并不知道是什么用户$this->vc = $vc;$discount = $this->vc->getDiscount();$usertype = $this->vc->getUserType();echo $usertype."商品价格：".$this->price*$discount;
    }
}$display = new Goods();$display ->run(new VipUser); //VIP用户商品价格：70.4

This example demonstrates a simple application of a PHP interface. In this example, the User interface implements the user's discount, and the VipUser class implements the specific discount coefficient. Finally, the product category Goods implements different user quotes based on the User interface.

Finally summarized:

The difference between abstract classes and interfaces

The interface is A special abstract class can also be regarded as a model specification. The general difference between an interface and an abstract class is as follows:

1. If a subclass implements an interface, it must implement all methods in the interface (whether needed or not); if it inherits an abstract class, it only needs to implement the required Just use the method.

2. If the method name defined in an interface changes, then all subclasses that implement this interface need to update the method name synchronously; and if the method name changes in an abstract class, the method name corresponding to its subclass will It is not affected, it just becomes a new method (relative to the old method implementation).

3. Abstract classes can only be inherited singly. When a subclass needs to implement functions that need to be inherited from multiple parent classes, interfaces must be used.

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