code: public function serialize()
  	{
  		$data = array
  		(
  			'id' => $this->id,
  			'username' => $this->username,
  			'password' => $this->password,
  			'admin' => $this->admin,
  			'disable' => $this->disable,
  			'start' => $this->start,
  			'stop' => $this->stop
  		);
  
  		return serialize($data);
  	}
docs: {@inheritdoc}