PHP后期静态绑定

class A
{
    public static function call()
    {
      echo "class A";
    } 

    public static function test()
    {
      self::call();
      static::call();
    }
}

class B extends A
{
    public static function call()
    {
      echo "class B";
    }
}

B::test();
// 输出 class A   class B

class A
{
    public function call()
    {
      echo "instance from A\n";
    } 

    public function test()
    {
      self::call();
      static::call();
    }
}

class B extends A
{
    public function call()
    {
      echo "instance from B";
    }
}

$b = new B();
$b->test();
// 输出 instance from A   instance from A