Detailed explanation of the differences between PHP object-oriented private, protected and public

This article mainly shares with you a detailed explanation of the differences between PHP object-oriented private, protected, and public. I hope it can help everyone.

        private     protected       public本类内     Y           Y              Y
子类内     N           Y              Y
外部       N           N              Y

Note:
In java, if no parameters are written in front of the attributes/methods
that is, public/protected/private are not written, It is also possible, friendly

In PHP, if public/protected/private are not written,
is understood as public. It is recommended to develop good habits and don’t write

class Human {
    private $name = 'zhangsan';    protected $money = 3000;    public $age = 28;    public function say() {
        echo &#39;我叫&#39;,$this->name,&#39;<br />&#39;;        echo &#39;我有&#39;,$this->money,&#39;元钱<br />&#39;;        echo &#39;我今年&#39;,$this->age,&#39;岁&#39;;
    }
}class Stu extends Human {
    private $friend = &#39;小花&#39;;    public function talk() {
        echo &#39;我叫&#39;,$this->name,&#39;<br />&#39;;        echo &#39;我有&#39;,$this->money,&#39;元钱<br />&#39;;        echo &#39;我今年&#39;,$this->age,&#39;岁<br />&#39;;        
    }
}$ming = new Stu();echo $ming->age,&#39;<br />&#39;; // 28echo $ming->friend; //出错：因为类外不能调用privateecho $ming->money; //出错：因为类外不能调用protected属性$ming->talk();/**
出错：
Notice: Undefined property: Stu::$name in 。。。
我有3000元钱
我今年28岁

分析原因: Undefined property: Stu::$name 这是说明:stu对象 没有name属性
但昨天说,私有的不是可以继承吗?
是可以继承过来,但系统有标记,标记其为父类层面的私有属性.
因此无权调用,导致此错发生.


可以分析出:
protected 可以在 子类内访问

protected能在子类访问,本类内能否访问?
答:当然可以

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