Object-oriented inheritance in PHP

Objectives of this article:

1. Understand the definition of inheritance

2. Master the benefits of inheritance

(1).Definition

   

Let’s look at the picture above carefully, and then do one thing to find out what they have in common

Common ground:

1. They all have some of the same attributes and methods

2. They are all human beings

Follow the definition of normal classes. If we want to implement the above two classes, we have to define them separately. All attributes and methods of the NBA player class, and then when defining the female anchor class, you have to write repeated attributes such as name, height, weight and eating methods. If there is another class called student, it means that these common The attributes and common methods have to be written again, and so on. The code will be similar in many places, which increases the redundancy of the code. Therefore, in order to solve this redundancy, in order to make the code more concise and reusable High, we can write these common attributes and methods together, and then let each class call this common attribute and method. Will it be more convenient to maintain and the code will be more concise? Then We call this approach inheritance

How to do it specifically, as shown below

We first create a "person" class, let this person Both have attributes and methods common to both classes, and then let both NBA players and female anchors inherit the "person" class

Concept: The inherited class is called the parent class, such as people, and the inherited class is called the subclass

Summary: What is inheritance? Inheritance is a method to improve the reusability of code and reduce the number of The redundancy of code is just like heredity in real life. Children will inherit part of their parents’ genes, so when you are born, you will have the common attributes and behaviors of humans

(2) Benefits of inheritance

1. Improve code reusability and save programming time and cost

The attributes and methods defined in the parent class do not require subclasses If the definition is repeated in a class, as long as the subclass inherits the parent class, it will have all the properties and methods in the parent class

2. All subclasses under the same parent class can be treated equally when calling them

For example, whether it is an NBA player or a female anchor, because they are all human beings, when we call them, we can directly call the method of the parent class, such as eating, regardless of whether the class is an NBA player or a female anchor

3. Subclasses can modify and adjust the class members defined by the parent class

a. We call it Overwrite

b. Once the subclass is modified, Execute according to the method defined by the subclass

This is equivalent to mutation

To learn anything, we must not only know the theory, but also have relevant theoretical practices. In fact, all theories are derived from practice. Yes, so sometimes I have repeatedly emphasized that although the theory is very abstract, everyone must also summarize it after they have certain practical experience, and summarize some concise and easy-to-understand "theory". After this habit is cultivated, I believe Everyone can understand a lot of knowledge more thoroughly, and at the same time, it is easier to grasp the essence of things, so that the ability to analyze problems will also be improved.

Okay, since we need to combine theory and practice, then next, we will conduct a practical demonstration through the code to see how inheritance is implemented in the code

( 3) Specific code

<?php
/***
 * 案例目标
 * 1.掌握继承的定义
   2.掌握继承的好处
 */
 //定义一个“人”类
class Human{
    public $name = "";//姓名
    public $height = "";//身高
    public $weight = "";//体重

    public function eat($food){
        echo $this->name."在吃".$food."<br/>";
    }
}
//女主播
class Anchors extends Human{
    public $name = "";
    public $stageName = "";
    public function __construct( $name,$stageName ){
        $this->name = $name;
        $this->stageName = $stageName;
    }
    public function singing(){
        echo "我是女主播，我会唱歌<br/>";
    }
    //重写方法eat
    public function  eat($food){
        echo "我是女主播，我是边唱歌边吃{$food}<br/>";
    }
}
//Nba球员类
 class NbaPlayer extends Human{
   //因为父类已经有了，所以就不需要再写了，通过extends来实现
    // public $name  = "";//姓名
    // public $height = "";//身高
    // public $weight = "";//体重

    public $team = "";//团队
    public $playerName = "";//球员号码

    public function __construct( $name,$height,$weight,$team,$playerName ){
        $this->name = $name;
        $this->height=$height;
        $this->weight = $weight;
        $this->team = $team;
        $this->playName = $playerName;
        echo "构造函数执行了,当前对象是{$this->name}<br/>";
    }
    
   
   //跑步
    public function run(){
        echo "跑步中<br/>";
    }
    //跳跃
    public function jump(){
        echo "跳跃<br/>";
    }
    //运球
    public function dribble(){
        echo "运球<br/>";
    } 
    //传球
    public function pass(){
        echo "传球<br/>";
    }
    //投篮
    public function shoot(){
        echo "投篮<br/>";
    }
    //扣篮
    public function dunk(){
        echo "扣篮<br/>";
    }
    //重写方法eat ，只要名称和父类一样就是代表重写了不一定参数也要保持一样
    public function eat($food){
        echo "我是Nba球员，我是站着吃饭，边吃{$food}边看球赛<br/>";
    }
 }
 //测试，NBA球员，没有直接定义name，身高，体重，现在输出一下看结果有没有
 //创建乔丹对象
 $jordon = new NbaPlayer("乔丹","1.98米","98公斤","公牛","23");
 //输出乔丹对象
 echo "名称= ".$jordon->name."<br/>";

 //测试，NBA球员，没有直接定义eat方法，现在输出一下看结果有没有
 echo $jordon->eat("苹果");
 //证明第二个好处，只要是个人就可以调用它的eat方法
 $linda = new Anchors("琳达","LD");
 echo $linda->eat("苹果");
 //测试第三个好处是否真实
 //思路1.为女主播和NBA球员2个类分别重写eat方法
//    2.再次执行2个对象的eat方法
//  会发现一旦子类重写了父类的方法，那么就会调用子类自己的方法了,这里就大家自己写下，因为上面我已经调用了eat方法，一旦重写了，上面的结果会变

?>

Through the demonstration of the above code, we summarize:

1. extends means inheritance. Through this keyword, the subclass can inherit the parent Class, sharing all attributes and methods of the parent class

2. Other features of inherited code:

● In the subclass constructor, it can also be accessed directly through $this->

● In PHP, only one class can be inherited after extends, and cannot be used to inherit multiple classes, otherwise an error will be reported

Summary:

This article In fact, there are only two goals. Knowing the definition and benefits of inheritance. Finally, we believe that we have a deeper understanding of the benefits of inheritance through code

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