title: CodeIgniter optional parameter
body: <p>I'm trying to use routing in CI to create a signup form</p>
  
  <p><code>signup</code> is re-routed to <code>user/signup</code></p>
  
  <p>But my signup function can contain a paramater: <code>function signup($type = 1)</code></p>
  
  <p>How can I make this optional via routing? I tried <code>$route['signup/?(:num)'] = 'user/signup/$1';</code>, but when going to <code>/signup</code> I'm getting a 404, only <code>/signup/1/</code> works.</p>