PHP 继承和静态方法和属性答案

【问题标题】：PHP Inheritance and Static Methods and PropertiesPHP 继承和静态方法和属性
【发布时间】：2011-11-10 00:47:19
【问题描述】：

可以说静态属性和方法在 PHP 中不能被继承吗？举几个例子会有帮助。

【问题讨论】：

【解决方案1】：

没有。这不是真的。 Static Methods and properties 将获得与非静态方法和属性相同的 inherited 并遵循相同的 visibility rules:

class A {
    static private $a = 1;
    static protected $b = 2;
    static public $c = 3;
    public static function getA()
    {
        return self::$a;
    }
}

class B extends A {
    public static function getB()
    {
        return self::$b;
    }
}

echo B::getA(); // 1 - called inherited method getA from class A
echo B::getB(); // 2 - accessed inherited property $b from class A
echo A::$c++;   // 3 - incremented public property C in class A
echo B::$c++;   // 4 - because it was incremented previously in A
echo A::$c;     // 5 - because it was incremented previously in B

最后两个是显着的区别。在基类中增加继承的静态属性也会在所有子类中增加它，反之亦然。

【讨论】：

【解决方案2】：

否（显然我在问题中看不到 not）。 public 和 protected 静态方法和属性按照您的预期继承：

<?php
class StackExchange {
    public static $URL;
    protected static $code;
    private static $revenue;

    public static function exchange() {}

    protected static function stack() {}

    private static function overflow() {}
}

class StackOverflow extends StackExchange {
    public static function debug() {
        //Inherited static methods...
        self::exchange(); //Also works
        self::stack();    //Works
        self::overflow(); //But this won't

        //Inherited static properties
        echo self::$URL; //Works
        echo self::$code; //Works
        echo self::$revenue; //Fails
    }
}

StackOverflow::debug();
?>

静态属性和方法遵循visibility 和inheritance 规则，如this snippet 所示。

【讨论】：