如何从子类访问父变量 [英] how to access parent variable from child class

问题描述

我有两个类一个父和另一个扩展，我需要使用main vars在扩展类。
例如

i have two classes one parent and the other extends , I need to use main vars in extended class. for example

class parentClass
{
    $this->value = null
    function __construct()
    {
        echo "im parent" ;
    }

}
class childClass extends parentClass
{

    function sayIt()
    {
        var_dump($this->value);
    }
}

$p = new parentClass ; 
$p->value = 500 ; 

$c = new childClass ; 
$c->sayIt(); // this output null ! i want it to output 500 , how i can do that

感谢

推荐答案

坏坏坏代码严格用于教育目的，我建议你拿一本关于面向对象编程的基本原理的书<

Bad Bad Bad The code is strictly for educational purpose i would advice you to get a book on basic Principles of Object Oriented programming

将您的变量设为静态可以通过子类访问

Making your variable static would make it accessible via the child class

class parentClass {
    public static $value = null;

    function __construct() {
        echo "patent called";
    }
}
class childClass extends parentClass {

    function sayIt() {
        var_dump(self::$value);
    }
}

$p = new parentClass();
parentClass::$value = 500;

$c = new childClass();
$c->sayIt();

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