instantiate derived class objects from within base class?

All, I get a fatal error when trying to create a new instance of a derived class from within a static member which exists in the parent base class. I think the problem is related to using this call: new self(); Because the 'self' refers to the parent object and not the derived class. See the code below and the error message which follows: ---------- 8< -------------------- 8< -------------------- 8< ---------- <?php // defines base functions and requires derived class to replace foo() class A { protected abstract function foo(); public static function bar() {

       $x = new self();
       $x->foo();

} } // defines foo() as it should, but base class doesn't know foo exists // when it references self() class B extends A { protected function foo() {

       echo "hello world";

} } // show how broken things are B :: bar(); ?> ---------- 8< -------------------- 8< -------------------- 8< ---------- PHP Fatal error: Class A contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (A::foo) in .../demo.php on line 9 How do I refer to the derived class from within the base class? Dante