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，请问最后的输出结果是如何得到的？

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，why?