title: WordPress: Widget checkbox option not storing the state
body: <p>I am having trouble to keep the state of Wordpress Widget option checkbox. Here is my code</p>
  
  <pre><code>&lt;label for="&lt;?php echo $this-&gt;get_field_id('display_name'); ?&gt;"&gt;&lt;input
  type="checkbox"
  id="&lt;?php echo $this-&gt;get_field_id('display_name'); ?&gt;"
  name="&lt;?php echo $this-&gt;get_field_name('display_name'); ?&gt;"
  &lt;?php checked(isset($display_name) ? $display_name : 0); ?&gt; /&gt; Display name&lt;/label&gt;
  </code></pre>
  
  <p>Also I want to know how can I use multiple checkbox group to store and retrieve data</p>