code: public function rename($key, $newkey)
      {
          if ($key === $newkey) {
              throw new Exception('ERR source and destination objects are the same');
          } elseif (!$this->storage->hasKey($key)) {
              throw new Exception('ERR no such key');
          }
  
          if ($this->storage->hasKey($newkey)) {
              $this->del($newkey);
          }
  
          $this->storage->rename($key, $newkey);
  
          return true;
      }
docs: StatusReply