PHP类继承的一段代码

class Bar {    
    public function test() {        
        $this->testPrivate();        
        $this->testPublic();    
    }    
    public function testPublic() {        
        echo "Bar::testPublic\n";    
    }        
    private function testPrivate() {        
        echo "Bar::testPrivate\n";    
    }
}
class Foo extends Bar {    
    public function testPublic() {       
         echo "Foo::testPublic\n";    
    }        
    private function testPrivate() {        
        echo "Foo::testPrivate\n";    
    }
}
$myFoo = new Foo();
$myFoo->test(); 
// Bar::testPrivate                 
// Foo::testPublic

来自php手册的一段代码

子类Foo的对象调用了test()方法，test()方法调用了$this->testPrivate();这个$this此时应该是子类的引用，按理说应该调用子类的testPrivate()方法，实际上却调用了父类的testPrivate()方法