PHP访问控制问题

abstract class base { 
    public function inherited() { 
        $this->overridden(); 
    } 
    private function overridden() { 
        echo 'base'; 
    } 
} 

class child extends base { 
    private function overridden() { 
        echo 'child'; 
    }
}
$test = new child();
$test->inherited();