title: WordPress - Add Yes/No to custom field if checkbox is checked
body: <p>I've created a custom field (type read only) with ACF Field for users (Label: &quot;Check Field Privacy&quot;; name &quot;privacy_field&quot;).</p>
  <p>In my website I add a form where there is a checkbox to confirm the reading of the website policy.
  This is the checkbox</p>
  <pre><code>&lt;p&gt;
  &lt;input type=&quot;checkbox&quot; name=&quot;foo_privacy_policy&quot; id=&quot;foo_privacy_policy&quot; class=&quot;checkbox&quot; /&gt;
  &lt;label for=&quot;foo_privacy_policy&quot;&gt;&lt;?php _e( 'I accept terms and.......', 'foo' ) ?&gt;
  &lt;/label&gt;
  </code></pre>
    </p>
  <p>I need to assign &quot;Yes&quot; to Check Privacy Field if the checkbox is checked and &quot;No&quot; if checkbox isn't checked</p>
  <p>I try with:</p>
  <pre><code>if ( isset($_POST['foo_privacy_policy']) ) {
      $privacy_field = &quot;YES&quot;; 
              }
  </code></pre>
  <p>It doesn't work...</p>