title: Trying to retrieve file from request with Silex/Symfony2
body: <p>I'm retrieving a POSTed file with:</p>
  
  <pre><code>$this-&gt;app-&gt;post(Extension::API_PREFIX . "profile/picture", array($this, 'post_profile_pic'))
        -&gt;bind('post_profile_pic');
  
  public function post_profile_pic(Request $request) {
      $response = $this-&gt;app-&gt;json(array(
          'file' =&gt; $request
      ));
      return $response;
  }
  </code></pre>
  
  <p>I'm using Postman to upload the file (see <a href="http://i.imgur.com/7d5Dqvf.png" rel="nofollow">screenshot</a>), but the request is empty:</p>
  
  <pre><code>{
      "file": {
          "attributes": { },
          "request": { },
          "query": { },
          "server": { },
          "files": { },
          "cookies": { },
          "headers": { }
      }
  }
  </code></pre>
  
  <p>Yet it obviously knows that there should be a file there. So how do I access the file?</p>