title: Custom field in XML is not saving parametars in DB
body: <p>This is code which creates custom field:</p>
  
  <pre><code>&lt;?php
  
  defined('_JEXEC') or die('Restricted access');
  
  class JFormFieldCustom extends JFormField {
  
      protected $type = 'Custom';
  
      protected function getInput() {
  
          $db = JFactory::getDbo();
  
          $query = $db-&gt;getQuery(true);
          $query = 'SELECT id, title FROM #__content';
          $db-&gt;setQuery($query);
          $rows = $db-&gt;loadObjectList();
  
          $result = '';
          foreach ($rows as $row) {
              $result .= '&lt;label&gt;' . $row-&gt;title  . '&lt;/label&gt;&lt;input type=checkbox name=article  value="' . $row-&gt;id .'"/&gt;';
          }
          return $result;
      }
  
  }
  ?&gt;
  </code></pre>
  
  <p>And the code into XML file:</p>
  
  <pre><code>&lt;field name="checkboxes" type="custom" default="" label="Articles" description="" /&gt;
  </code></pre>
  
  <p>The problem is that nothing is saved as params into DB. What is wrong here?</p>