search
HomeBackend DevelopmentPHP TutorialPHP封装与继承实例

封装

把成员方法和成员属性封装到类中,隐藏属性和方法实现的细节,通过public、protected、private等限定类成员的访问权限,数据被保护在内部,只通过被授权的成员方法才可以操作,尽可能的对成员进行封装。
public:方法或者属性在任何作用域下都可以访问到,而且是默认的,如果没有为一个属性或方法指定访问修饰符,它将是public。
protected:本类和子类可以访问,外部对象不可以调用。

private:只能在本类访问,子类与外部对象都不可能调用。经过private标记的方法或者属性可以在继承类中重新定义,每一个类只能看到它自己定义的私有方法。
这三个修饰符从作用范围上来讲应该像这样从大到小排序:public→protected→private之所以说是在作用范围上,是因为类把一些属性和方法进行了封装,这个封装就决定了数据的“可见性”,这样我们在类的外面不能够随意修改所定义的属性和方法而只能够进行调用,这就是封装的好处,同时也提高了安全性。

我们给出代码示例:
class myClass{

public$public="Public";//public属性

protected$protected="Protected";//protected属性
private$private="Private";//private属性

function say_Hello(){//public属性

//只是举例说明,自行添加内容
}

$obj=new myClass();
echo$obj->public;

//echo$obj->protected;
//echo$obj->private;

通过运行以上示例我们得到一个“Public”,但当你把//echo$obj->private;的注释去掉时,你会得到一下如下的错误:Fatal error:Cannot access protected property myClass::$protected in E:apachehtdocsexamplefile.php on line 13。可以看到我们不能随意去访问类的属性定义,我们在“外面”是不知道这个类中到底有那些成员,因为这些成员对于其他的类可能是不可见的。当然如果我们一定要访问或者修改定义为“私有”的属性时,也可以使用PHP所提供的系统方法:_get()和_set()。

继承

可以使一个类继承并拥有另一个已经存在类的成员属性和方法,被继承的类称为父类或基类,继承类为子类。通过extends关键字实现继承关系。通俗来说,要有继承就得有一个“根源”,这“根源”你可能想像你以后生了儿子或者女儿,他们会从你这里得到一些“东西(属性和方法)”,这样你的“后代”就是持有你(根源)所有的一些特征了。
产生“根源”类(父类或者基类)
语法:class father{
}

产生“后代”(子类)
语法:class son extends father{
}
PHP extends类继承示例代码:
class father{
protected$name;
function__construct($name){//构造函数
$this->name=$name;
}
function work(){
echo"{$this->name}我在工作;
}
function__destruct(){}//析构函数
}
class son extends father{//继承父类
function play(){
echo"{$this->name}我在玩游戏;
}
}
$my_father=new father(“爸爸”);//创建父类对象
$my_father->work();
$my_son=new son(“儿子”);
$my_son->work();
$my_son->play();
解析:在父类father里,我们定义了一般的属性和方法,然后定义子类。你可能发现在子类里内是没有构造函数和析构函数的,因为子类是继承了父类的所有方法,所以可以调用$my_son->work();这就是PHP类的继承了。另外要注意:PHP不能多层继承,如:class A extends B extends C,这样的继承在PHP中是无效的,PHP里只有单继承,不能多继承,需要其他办法变相“实现”多继承。

更多新体验,欢迎试用JetBrains旗下的各种Web开发工具(包括PHPIDE)。另外还有5折限时抢购和免费领iPhone?6、iPad?air等好礼!


Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
PHP and Python: Different Paradigms ExplainedPHP and Python: Different Paradigms ExplainedApr 18, 2025 am 12:26 AM

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP and Python: A Deep Dive into Their HistoryPHP and Python: A Deep Dive into Their HistoryApr 18, 2025 am 12:25 AM

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

Choosing Between PHP and Python: A GuideChoosing Between PHP and Python: A GuideApr 18, 2025 am 12:24 AM

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP and Frameworks: Modernizing the LanguagePHP and Frameworks: Modernizing the LanguageApr 18, 2025 am 12:14 AM

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHP's Impact: Web Development and BeyondPHP's Impact: Web Development and BeyondApr 18, 2025 am 12:10 AM

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

How does PHP type hinting work, including scalar types, return types, union types, and nullable types?How does PHP type hinting work, including scalar types, return types, union types, and nullable types?Apr 17, 2025 am 12:25 AM

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values ​​and handle functions that may return null values.

How does PHP handle object cloning (clone keyword) and the __clone magic method?How does PHP handle object cloning (clone keyword) and the __clone magic method?Apr 17, 2025 am 12:24 AM

In PHP, use the clone keyword to create a copy of the object and customize the cloning behavior through the \_\_clone magic method. 1. Use the clone keyword to make a shallow copy, cloning the object's properties but not the object's properties. 2. The \_\_clone method can deeply copy nested objects to avoid shallow copying problems. 3. Pay attention to avoid circular references and performance problems in cloning, and optimize cloning operations to improve efficiency.

PHP vs. Python: Use Cases and ApplicationsPHP vs. Python: Use Cases and ApplicationsApr 17, 2025 am 12:23 AM

PHP is suitable for web development and content management systems, and Python is suitable for data science, machine learning and automation scripts. 1.PHP performs well in building fast and scalable websites and applications and is commonly used in CMS such as WordPress. 2. Python has performed outstandingly in the fields of data science and machine learning, with rich libraries such as NumPy and TensorFlow.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
Will R.E.P.O. Have Crossplay?
1 months agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

WebStorm Mac version

WebStorm Mac version

Useful JavaScript development tools

Dreamweaver Mac version

Dreamweaver Mac version

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)