title: Add the option null to the dropdown dynamic in codeigniter
body: <p>I have added a dropdown dynamic in codeigniter</p>
  
  <pre><code>echo form_dropdown('mydrop',$options);
  </code></pre>
  
  <p>The options are called of a query in the database.  How can I add at first of the options, the option:</p>
  
  <pre><code>value="" Select an option with codeigniter
  </code></pre>
  
  <p>Thanks.</p>