code: function getDelta($cursor = null, $pathPrefix = null)
      {
          Checker::argStringNonEmptyOrNull("cursor", $cursor);
          Path::checkArgOrNull("pathPrefix", $pathPrefix);
  
          $response = $this->doPost($this->apiHost, "1/delta", array(
              "cursor" => $cursor,
              "path_prefix" => $pathPrefix));
  
          if ($response->statusCode !== 200) throw RequestUtil::unexpectedStatus($response);
  
          return RequestUtil::parseResponseJson($response->body);
      }
docs: A way of letting you keep up with changes to files and folders in a user's Dropbox.
  
  @param string|null $cursor
  If this is the first time you're calling this, pass in `null`.  Otherwise,
  pass in whatever cursor was returned by the previous call.
  
  @param string|null $pathPrefix
  If `null`, you'll get results for the entire folder (either the user's
  entire Dropbox or your App Folder).  If you set `$path_prefix` to
  "/Photos/Vacation", you'll only get results for that path and any files and folders
  under it.
  
  @return array
  A <a href="https://www.dropbox.com/developers/core/docs#delta">delta page</a>, which
  contains a list of changes to apply along with a new "cursor" that should be passed into
  future `getDelta` calls.  If the "reset" field is `true`, you
  should clear your local state before applying the changes.  If the "has_more" field is
  `true`, call `getDelta` immediately to get more results, otherwise
  wait a while (at least 5 minutes) before calling `getDelta` again.
  
  @throws Exception