title: How to determine whether $addToSet inserted new value or not?
body: <p><code>$addToSet</code> inserts new value into array if that value isn't already in that array and that's cool but the update method always returns the same response in both cases (when the value is already there and when it's not), which looks something like this:</p>
  
  <pre><code>Object {updatedExisting: true, n: 1, connectionId: 34, err: null, ok: 1}
  </code></pre>
  
  <p>Now I need to determine whether the last query actually inserted anything into the array or not. I use php driver.</p>