PHP:属性可见性、静态等 [英] PHP: Property visibilty, static, etc

问题描述

我知道这是一个非常愚蠢的问题，但我并没有真正理解一些东西，我每天都在使用它们，但我不确定它们是如何工作的.

I know that this is a real stupid question, but I don't really understand something, I use them everyday, but I'm not sure how they work.

class Bootstrap
{
public static $frontController = null;
public static $root = '';

公共静态、受保护、公共...所有这些之间的区别是什么?什么时候最好使用每一个...

What's the diff between public static, protected, public...all of them? and when it's best to use each of one...

最好的问候

推荐答案

• static 表示该值是通过 self::$var 而不是 $this->var 访问的，不是特定于实例的(即它也可用于静态方法)，因此非常适合单例和类似模式
• a public var 可以从任何地方访问，即从类内部和外部
• protected var 只能从类内部以及从定义 var 的类继承的类访问
• a private var 只能从类内部访问
• static means the value is accessed via self::$var instead of $this->var, is not instance-specific (i.e. it's also available in static methods) and thus ideal for singletons and similar patterns
• a public var is accessible from everywhere, i.e. both from inside the class and outside
• a protected var is only accessible from inside the class and from classes inheriting from the class where the var is defined
• a private var is only accessible from inside the class

既然您问的是 OOP 基础知识，这里还有一些值得解释的关键字:

Since you are asking about OOP basics, here are some more keywords worth explaining:

• abstract 类不能被实例化，只能作为基类使用；包含抽象方法的类必须是抽象的，从抽象类继承的类必须是抽象的，除非基类的所有抽象方法都实际实现了
• final 类不能继承
• an abstract class cannot be instantiated but only used as a base class; a class containing abstract methods must be abstract and a class inheriting from an abstract class must be abstract unless all abstract methods of the base class are actually implemented
• a final class cannot be inherited from

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