PHP继承和LSB问题

Question

我有以下问题：

<?php

/**
 * Mother class defining static methods/attribute
 */
class A
{
    public static $_greetings = 'Nothing';

    public static function hi()
        {
            $c = get_called_class();
            echo $c.' says '.$c::$_greetings.PHP_EOL;
        }

    public static function set($classname)
        {
            $c = get_called_class();
            $g = $classname::$_greetings;

            echo 'Setting '.$c.'::_greetings to '.$g.PHP_EOL;
            $c::$_greetings = $g;
        }
}

/**
 * Children using inherited static method
 */
class C1 extends A
{
    public function say() { self::hi(); }
}

class C2 extends A
{
    public function say() { self::hi(); }
}

/**
 * Data containers
 */
class D1
{
    public static $_greetings = 'Hello World!';
}

class D2
{
    public static $_greetings = 'Ola Chica!';
}

// ------------------------------------------------------------------------

/**
 * The great misunderstanding...
 */
C1::set( 'D1' );
C2::set( 'D2' );

$c1 = new C1();
$c2 = new C2();

$c1->say();
$c2->say();

echo C1::$_greetings.PHP_EOL;
echo C2::$_greetings.PHP_EOL;

简单地说，A定义了一个打印静态消息$_greetings的方法。此消息将使用A::set( classname )进行设置，这将输入包含静态参数$_greetings的类的名称。然后是两个子程序，它们定义了自己的方法say()，使用继承的静态hi()来打招呼。我预计产出如下：

Setting C1::_greetings to Hello World!
Setting C2::_greetings to Ola Chica!
C1 says Hello World!
C2 says Ola Chica!
Hello World!
Ola Chica!

但我得到的是：

Setting C1::_greetings to Hello World!
Setting C2::_greetings to Ola Chica!
C1 says Ola Chica!
C2 says Ola Chica!
Ola Chica!
Ola Chica!

我想知道为什么.！？提前感谢那些愿意花时间理解问题的人:)

Answer 1

我可以在这里找到答案，尽管问题的措辞不一样：PHP 5.3: Late static binding doesn't work for properties when defined in parent class while missing in child class

在我的小例子中，问题来自这样一个事实:除非另有规定(见下面的说明)，静态变量的存储对于“家庭”类(即母亲和所有子类)是相同的。要确保每个类都有自己的存储空间，只需在子类中重新声明相同的静态变量，如下所示：

/**
 * Children using inherited static method
 */
class C1 extends A
{
    public static $_greetings;
    public function say() { self::hi(); }
}

class C2 extends A
{
    public static $_greetings;
    public function say() { self::hi(); }
}

将其返回到前面的示例中，输出与预期的完全相同：

Setting C1::_greetings to Hello World!
Setting C2::_greetings to Ola Chica!
C1 says Hello World!
C2 says Ola Chica!
Hello World!
Ola Chica!