Abstract classes and interfaces

In PHP, abstract classes can be declared through the abstract keyword. Sometimes we need a class to have certain public methods. In this case, we can use interface technology

1, create an animal class

##Animal.class.php code is as follows:

<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2018/3/3 0003
 * Time: 下午 2:13
 */
abstract class Animal{
    public $gender;  //性别
    public $size;      //尺寸
    public function __construct($gender,$size){
        $this->gender=$gender;
        $this->size=$size;
    }
    //限制非抽象类都需要调用此方法
    abstract protected function getGender();
    //final要求每个子类必须存在该方法并且不能重写
    final public function getSize(){
        return $this->size;
    }
}

2, create a dog class

<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2018/3/3 0003
 * Time: 下午 2:20
 */
header('content-type:text/html;charset=utf8');
require './Animal.class.php';
class Dog extends Animal {
    /**
     * @return mixed
     */
    public function getGender()
    {
        return "'$this->gender'狗";
    }
}
$dog=new Dog('公','大');
echo $dog->getSize();
echo $dog->getGender();

The running results are as follows:

##3, create a cat classCat.class.php code is as follows:

<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2018/3/3 0003
 * Time: 下午 2:22
 */
header('content-type:text/html;charset=utf8');
require './Animal.class.php';
class Cat extends Animal { 
    public function getGender()
    {
        return "'$this->gender'猫";
    }
}
$dog=new Cat('母','小');
echo $dog->getSize();
echo $dog->getGender();

<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2018/3/3 0003
 * Time: 下午 2:34
 */
header('content-type:text/html;charset=utf8');
//定义usb接口
interface usb{
    public function connect(); //连接
    public function transfer(); //传输
    public function disconnect(); //断开
}
class mp3 implements usb{
    public function connect()
    {
        // TODO: Implement connect() method.
        echo "连接...<br>";
    }
    public function transfer()
    {
        // TODO: Implement transfer() method.
        echo "传输...<br>";
    }
    public function disconnect()
    {
        // TODO: Implement disconnect() method.
        echo "断开...<br>";
    }
}
$mp3=new mp3();
$mp3->connect();
$mp3->transfer();
$mp3->disconnect();

operation result: