php anonymous class extends dynamic

Question

anyone of you know how to get effect like in these code

 public function create(SomeInterface $obj)
 {
     $class = get_class($obj);
     return new class extends $class {
        //some magic here
     }
 }

Obvious that code will not work in PHP. $obj can be an instance of many different classes. I want to get an instance of class extending the $obj. (It will give me an ability to overload some basic methods)