Reading static variables in child-classes failing?

Hi, all I'm currently testing something in PHP with static variables ... Do you know, why I can't read static variables of a child class, even so the variable is protected or public? Here's an example: class A { protected static $foo = "bar"; } class B { public function readFoo() { return self::$foo; } } When now calling B::readFoo, I get the following error: var_dump((new B())->readFoo()); PHP Fatal error: Access to undeclared static property: B::$foo in php shell code on line 1 PHP Stack trace: PHP 1. {main}() php shell code:0 PHP 2. B->readFoo() php shell code:1 Fatal error: Access to undeclared static property: B::$foo in php shell code on line 1 Call Stack: 86.2643 231224 1. {main}() php shell code:0 86.2666 231352 2. B->readFoo() php shell code:1 Tested using PHP 5.5.6 Bye, Simon