受保护的静态成员变量

Question

I've recently been working on some class files and I've noticed that the member variables had been set in a protected static mode like protected static $_someVar and accessed like static::$_someVar.

I understand the concept of visibility and that having something set as protected static will ensure the member variable can only be accessed in the super class or derived classes but can I access protected static variables only in static methods?

Thanks

Answer 1

If I understand correctly, what you are referring to is called late-static bindings. If you have this:

class A {
   static protected $_foo = 'bar';

   static public function test() {
      echo self::$_foo;
   }
}

class B extends A {
   static protected $_foo = 'baz';
}

B::test(); // outputs 'bar'

If you change the self bit to:

echo static::$_foo;

Then do:

B::test(); // outputs 'baz'

Because self refers to the class where $_foo was defined (A), while static references the class that called it at runtime (B).

And of course, yes you can access static protected members outside a static method (i.e.: object context), although visibility and scope still matters.