interface in php

* Interface

* 1. Use the keyword: interface

* 2. Class is the template of the object, and the interface is the template of the class

* 3. Look at the interface It is a special class

* 4. The methods in the interface are only declared but not implemented, just like abstract classes

* 5. The methods in the interface must be public and support static

* 6. Class constants const can be declared in the interface, but they are not allowed to be overridden by classes or sub-interfaces

* 7. Use the implements keyword to implement an interface with a class

* 8 .A class can implement multiple interfaces, separated by commas

* 9. Interfaces can also use the keyword extends to inherit

* 10. A class can have multiple interfaces When using an interface, methods cannot have the same name

//Declare the interface: Animal

if (!interface_exists('Animal')) {
    interface Animal
    {
        //接口常量
        const status = 'viable'; //能存活的
        
        //接口方法:饲养时吃什么
        public function feeding($foods);
    }
}
//声明类Cat,并实现接口Animal
if (interface_exists('Animal')) {
    class Cat implements Animal
    {
        private $name = '猫';
        
        //在类中必须实现接口中的方法feeding()
        public function feeding($foods)
        {
            return $this->name.'吃'.$foods;
        }
    }
}
//实例化Dog类,
echo (new Cat())->feeding('老鼠');
echo &#39;<hr>&#39;;
//再定义一个接口:动物的特性
if (!interface_exists(&#39;Feature&#39;)) {
    interface Feature
    {        
        //接口方法
        public function hobby($hobby);
    }
}
//声明一个类Dog,实现了二个接口: Animal,Feature
if (interface_exists(&#39;Animal&#39;) && interface_exists(&#39;Feature&#39;)) {
    class Dog implements Animal, Feature
    {
        private $name = &#39;狗&#39;;
        
        //必须实现接口Animal中的feeding()方法
        public function feeding($foods)
        {
//            return $this->name.&#39;吃&#39;.$foods;
            //改成链式
            echo  $this->name.&#39;吃&#39;.$foods;
            return $this;
        }
        
        //必须实现接口Feature中的hobby()方法
        public function hobby($hobby)
        {
//            return $hobby;
            
            //改成链式
            echo $hobby;
            return $this;
        }
    }
}

//Instantiate the Dog class

echo (new Dog())->feeding('肉');
echo (new Dog())->hobby('忠诚,勇敢,不离不弃~~');

//Think about how to combine the above two Change a method call to a chain?

//Note: Comment out the above instantiation call statement first, otherwise the following chain call will not take effect

(new Dog)->feeding('骨头')->hobby(',可爱,温顺,听话~~');

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