title: Laravel only validate items that are posted and ignore rest of validation array
body: <p>For a project with Laravel 4.1 I have a little UI issue I'd like to solve.</p>
  
  <p>Some inputs make an ajax call to laravel on blur and that works fine. It simply sends it's value. In laravel I then check with the validator. </p>
  
  <pre><code>public function validate() {
          if(Request::ajax()) {
              $validation = Validator::make(Input::all(), array(
                  'email' =&gt; 'unique:users|required|email', 
                  'username' =&gt; 'required'
              ));
              if($validation-&gt;fails()) {
                  return $validation-&gt;messages()-&gt;toJson();
              }
              return "";
          }
          return "";
      }
  </code></pre>
  
  <p>Although this works, the json string also contains fields I have no need to check. To be precise this is the feedback I get:</p>
  
  <pre><code>{"email":["The email field is required."],"username":["The username field is required."]}
  </code></pre>
  
  <p>But seeing it is on blur I only want the one I'm actually checking in return. So if i'm blurring email I want a return of:</p>
  
  <pre><code>{"email":["The email field is required."]}
  </code></pre>
  
  <p>Now I know it's obviously because my array contains multiple fields, but I don't feel like writing a complete validation for each possible input I ever make.</p>
  
  <p>My question is: can I somehow only get a return of the post values that are actually posted, even though the value might be null and not get rest of the array back.</p>