[英]PHP Inheritance and Static Methods and Properties
是否可以安全地说静态属性和方法不能在PHP中继承? 一些例子会有所帮助。
不,那不是真的。 静态方法和属性将与非静态方法和属性一样继承 ,并遵循相同的可见性规则:
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
最后两个是显着的差异。 增加基类中的继承静态属性也会在所有子类中递增它,反之亦然。
不(显然我看不到问题中没有 )。 public
和protected
静态方法和属性将按照您的预期继承:
<?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();
?>
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