title: Laravel 5 multiple select() in query builder
body: <p>In laravel 5.1, I want to do like</p>
  
  <pre><code>$myTable = MyTable-&gt;select('firstField');
  
  if ($somethingTrue) {
      $myTable-&gt;select('secondField');
  }
  
  $myTable-&gt;get();
  </code></pre>
  
  <p>where I want both firstField &amp; secondField to be selected.<br>
  Of course the code above is not working, i.e. only the secondField is selected in the end.<br>
  <br>
  Is there any function provided by query builder class that can do exactly what I want?</p>