PHP Inheritance

PHP OOP Inheritance （PHP OOP继承）

Inheritance is a fundamental concept in Object-Oriented Programming (OOP) that allows developers to create new objects from existing ones, inheriting all its properties and methods. In PHP, inheritance is implemented using the extends keyword. In this article, we’ll explore PHP OOP inheritance in depth and understand how it can be used to simplify your code and create more maintainable applications. （继承是面向对象编程（ OOP ）中的一个基本概念，允许开发人员从现有对象中创建新对象，继承其所有属性和方法。在PHP中，继承使用extends关键字实现。在本文中，我们将深入探讨PHP OOP继承，并了解如何使用它来简化代码并创建更易于维护的应用程序。）

What is Inheritance? #

What is Inheritance? （什么是继承？）

Inheritance is a feature of OOP that allows developers to create new classes based on existing ones. The newly created class inherits all the properties and methods of the original class, also called the base or parent class. Inheritance is used to create a hierarchy of classes, where subclasses inherit the properties and methods of the parent class, and can also add new properties and methods of their own. （继承是OOP的一项功能，允许开发人员基于现有类创建新类。新创建的类继承原始类的所有属性和方法，也称为基类或父类。继承用于创建类的层次结构，其中子类继承父类的属性和方法，还可以添加自己的新属性和方法。）

Benefits of Inheritance #

Benefits of Inheritance （继承的好处）

There are several benefits of inheritance in PHP OOP, including:

• Reusability: Reuse the properties and methods of existing classes, avoiding the need to write new code for similar objects.

• Code Maintainability: Makes code more organized and easier to maintain by reducing code duplication and promoting code reuse.

• Polymorphism: Ability to use objects of different classes interchangeably, through inheritance.

• Abstraction: Encapsulation of properties and methods in a parent class, hiding the implementation details and making it easier to use subclasses.

PHP OOP Inheritance Syntax #

PHP OOP Inheritance Syntax （PHP OOP继承语法）

The syntax of inheritance in PHP is simple. To create a subclass, you use the extends keyword, followed by the name of the parent class. For example:

class ChildClass extends ParentClass {
   // Class body
}

The subclass ChildClass inherits all the properties and methods of the parent class ParentClass. To access the properties and methods of the parent class, you use the parent keyword. （子类ChildClass继承父类ParentClass的所有属性和方法。要访问父类的属性和方法，请使用parent关键字。）

Overriding Parent Methods #

Overriding Parent Methods （覆盖父方法）

Inheritance allows subclasses to override parent class methods, which means they can provide a new implementation of the method. To override a parent class method, you simply declare a new method with the same name in the subclass. For example:

class ParentClass {
   public function displayMessage() {
       echo "Hello from ParentClass";
   }
}

class ChildClass extends ParentClass {
   public function displayMessage() {
       echo "Hello from ChildClass";
   }
}

In this example, the ChildClass overrides the displayMessage method of the ParentClass. To access the parent class method, you can use the parent keyword. For example:

class ChildClass extends ParentClass {
   public function displayMessage() {
       parent::displayMessage();
       echo "Hello from ChildClass";
   }
}

PHP OOP Inheritance Example #

PHP OOP Inheritance Example （PHP OOP继承示例）

Let’s look at a real-world example of how inheritance can be used in PHP OOP. Consider a scenario where you have a Vehicle class with properties such as make, model, and year. You can then create a Car class that inherits from the Vehicle class, adding a new property fuelType. （让我们看一个真实的示例，了解如何在PHP OOP中使用继承。考虑一个场景，其中您有一个包含品牌、型号和年份等属性的车辆类。然后，可以创建继承自Vehicle类的Car类，添加新的属性fuelType。）

<?php

class Vehicle
{
   public $make;
   public $model;
   public $year;

   public function displayDetails()
（公共函数displayDetails ()）
   {
       echo "Make: " . $this->make . "\n";
       echo "Model: " . $this->model . "\n";
       echo "Year: " . $this->year . "\n";
   }
}

class Car extends Vehicle
{
   public $fuelType;
   public function displayDetails()
（公共函数displayDetails ()）
   {
       parent::displayDetails();
       echo "Fuel Type: " . $this->fuelType . "\n";
   }
}

In this example, the Car class inherits the properties and methods of the Vehicle class, but also adds a new property fuelType. The displayDetails method of the Car class also overrides the method of the same name in the Vehicle class, adding the output of the fuelType property. （在此示例中， “Car”类继承了“Vehicle”类的属性和方法，但也添加了新的属性“fuelType”。“Car”类的“displayDetails”方法也会重写“Vehicle”类中同名的方法，从而添加“fuelType”属性的输出。）

Conclusion #

Conclusion （小结）

Inheritance is a fundamental concept in PHP OOP, allowing developers to create new objects from existing ones, inheriting all their properties and methods. Inheritance helps promote code reuse, maintainability, and abstraction, making it an essential tool for developing PHP applications. In this article, we explored PHP OOP inheritance in detail, including its syntax, benefits, and an example of how it can be used in real-world applications. （继承是PHP OOP中的一个基本概念，允许开发人员从现有对象创建新对象，继承其所有属性和方法。继承有助于促进代码重用、可维护性和抽象性，使其成为开发PHP应用程序的重要工具。在本文中，我们详细探讨了PHP OOP继承，包括其语法、优势以及如何在实际应用中使用的示例。）