title: Which HTTP response code to send on unhandled request
body: <p>I have a PHP application that has a router that should have two default handlers for <code>401 Unauthorized</code> and <code>404 Not Found</code>.</p>
  
  <p>But it could happen that no handlers were set for those two cases. In that case, I need to have a default response that tells <code>Request Unhandled</code>, I have set it to the response code <code>400 Bad Request</code>, but I feel like its not truly appropriate.</p>
  
  <p>What response code should I use for a unhandled request?</p>