title: Getting all items in the collection mapWithKeys
body: <p>I have: </p>
  
  <pre><code>$collection=Event::all();
  $keyed = $collection-&gt;mapWithKeys(function ($item) {
                  return ['title' =&gt; $item['name'], 'start' =&gt; $item['event_date']];
     });
  </code></pre>
  
  <p><code>$keyed-&gt;all()</code> is returning only last item in the collection with changed keys:</p>
  
  <pre><code>Array
  (
      [title] =&gt; New Year
      [start] =&gt; 2018-01-01
  )
  </code></pre>
  
  <p>How do i get all events with changed keys?</p>