title: Eloquent with not working
body: <p>Hello I am having this problem with the laravel eloquent with.
  This code (in the docs) <code>$debtHistory = DebtHistory::with('user.firstname')-&gt;get();</code> seems to not work, because it returns something lik <code>Call to undefined relationship [firstname] on model [App\User].</code> what am I doing wrong here? Any idea? Thank you guys. :)</p>
  
  <p>Note: If this helps.</p>
  
  <p>I actually have an alternative method but I would like to do it in one query. This code my help you to know what I am trying to do.</p>
  
  <pre><code>$debtHistory = DebtHistory::whereBetween('created_at',[$filterData['from'], $filterData['to']])-&gt;where('amount', '&gt;', '0')-&gt;get();
  $excelData = [];
  foreach($debtHistory as $history) {
       array_push($excelData, ['Name' =&gt; $history-&gt;user-&gt;firstname .' '. $history-&gt;user-&gt;lastname, 'Debt' =&gt; $history-&gt;amount, 'Date' =&gt; Carbon::parse($history-&gt;created_at)-&gt;format('Y-m-d')]);
  }
  </code></pre>
  
  <p>I want to do that process in a eloquent model query is that possible?</p>