If your on the response to the post and you refresh it is going to resubmit, normal behavior. Redirect away to stop a resubmit.

Normal behavior? On my common forms i just unsetted $_POST and the problem was gone.

Sharping said:

Normal behavior? On my common forms i just unsetted $_POST and the problem was gone.

If you press refresh in a browser it will 'normally' do the last request. If it was a post request then that same post will be resubmitted regardless of whether you unset $_POST (post will be created each request). Thats why when you are finished with a post request you should redirect away to a get request. That way when you press refresh and it will only redo the new redirected get request.

Yes just redirect back with a status message, or to a new page (also with status message).

return Redirect::back()->withStatus('Form submitted!');