What does inheritance of php classes mean? Analysis of inheritance of php class-PHP Tutorial-php.cn

In PHP, the inheritance of PHP classes is an important content and a relatively difficult part to understand. So how do we learn PHP class inheritance? Just like heredity in human life, inheritance in the PHP programming world is just like heredity in the human world. Isn’t it easier to understand this way? So let’s analyze the inheritance of PHP classes in detail below.

First of all, after understanding some living principles of inheritance, I would like to see if the inheritance of PHP classes is no longer so mysterious. Maybe it’s not mysterious in the first place because we ourselves are too complicated. In order to have inheritance, there must be a "root". For this "root", you may imagine that if you give birth to a son or daughter in the future, they will get some "things (properties and methods)" from you, so that your "descendants" will continue to inherit. Has all the characteristics of your (roots). Let's describe how this is expressed in PHP's object-oriented language through grammar (it can't be as direct as humans, get married, and your offspring will be produced after a while)

1. Generate "roots" Class (parent class or base class)

Syntax:

class father{ }

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1. Generate "descendants" (subclasses)

Syntax:

class son extends father{ }

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Description: The parent class is just an ordinary class. If you want to have descendants, you only need to add the extends keyword after the ordinary class. In this way, your subclass only has all the attributes and methods of the parent class. It's actually that simple.

Let's do something practical. After all, defining a parent class and subclass in the inheritance of PHP classes is to complete a certain task! The task here is relatively monotonous. Take people as an example. People have names (attributes), and they have to sleep and eat (methods). Let's use this basic task to complete the knowledge in this section.

< ?php class father{ protected $name; function __construct($name){ $this->name=$name; } function __destruct(){ echo "< p>{$this->name}也是要死的< br/>< /p>"; } //这个就是所谓的构造函数，用来初始化 function go_to_sleeping(){ echo "< p>{$this->name}想睡觉.< /p>"; } function eat(){ echo "< p>{$this->name}想吃饭.< /p>"; } } class son extends father{ function playing(){ //小孩子会很调皮的,当然他也是要吃要睡的生物 echo "< p>{$this->name}正在捣蛋...< /p>"; } } $your_father=new father("老爸"); $your_father->go_to_sleeping(); $your_father->eat(); $my_son=new son('宝贝'); $my_son->go_to_sleeping(); $my_son->eat(); $my_son->playing(); ?> < ?php class father{ protected $name; function __construct($name){ $this->name=$name; } function __destruct(){ echo "< p>{$this->name}也是要死的< br/>< /p>"; } //这个就是所谓的构造函数，用来初始化 function go_to_sleeping(){ echo "< p>{$this->name}想睡觉.< /p>"; } function eat(){ echo "{$this->name}想吃饭.
"; } } class son extends father{ function playing(){ //小孩子会很调皮的,当然他也是要吃要睡的生物 echo "< p>{$this->name}正在捣蛋...< /p>"; } } $your_father=new father("老爸"); $your_father->go_to_sleeping(); $your_father->eat(); $my_son=new son('宝贝'); $my_son->go_to_sleeping(); $my_son->eat(); $my_son->playing(); ?>

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Analysis: In our first example of using inheritance, we use the constructor mentioned in the PHP constructor and the keywords in the PHP class package. If there is anything you don’t understand, just ask Go check it out! I don’t want to say any more. I didn’t want to sleep at noon. Let’s talk about this little program.

In the father of the class, we define general characteristics, such as the person's name, what the person needs to eat and sleep, and then in its subclass (descendant) we define a personalized method (playing), After all, there are differences between people. We use the constructor to initialize the name, and of course we use the destructor to "destroy" the object. But you may not find that there are no constructors and destructors in the subclass, so the subclass inherits the parent All methods, otherwise how can you call $my_son->go_to_sleeping(); like this? This is the inheritance of the PHP class.