مشکل در تابع set__

number = 500;
               }

               public function __get($name) {
                   return $this->{$name};
               }

               public function __set($name, $value) {
                   switch ($name) {
                       case '10':
                           $this->number = $value;

                           break;
                       case '20':
                           echo 'number 20 is bigger!';
                           break;
                       default :
                           echo 'Success';
                           break;
                   }
                   return $name;
               }

               public function show() {
                   echo '
' . $this->number . '
';
               }

           }

           $p = new test();
           //$p->show();
           echo $p->number;

           $p->number = 10;
           echo $p->number;
           ?>