如何做PHP嵌套类或嵌套方法？

class MyClass {
    public function myMethod() {
        $nestedMethod = function() {
            echo "This is a nested method.";
        };

        $nestedMethod();
    }
}

$obj = new MyClass();
$obj->myMethod();

class OuterClass {
    public function createInnerClass() {
        return new class {
            public function innerMethod() {
                echo "This is an inner method.";
            }
        };
    }
}

$outer = new OuterClass();
$inner = $outer->createInnerClass();
$inner->innerMethod();