Can't Get Checkbox Group Values in Email

I seem to be unable to get checkbox group values via UE. As a test, I created a very simple form using FB, which can be seen at test4.php. Using FB, I defined only two "Lines", where Line 1 is Name (a text field) and Line 2 is a Checkbox Group with three items that I labeled Item 1, Item 2, and Item3. In FB I set the "size" of the Checkbox Group to be One Column so that each item will appear on a separate line on the screen.

Then using UE to setup the email, in the Body tab I setup the four items for the email in the HTML editor part of this tab using DW, as shown in the online tutorial (i.e., binding the form elements to the correct parts of the page that I had just created). The PHP coded listed below is the resulting code generated. (I see this code when I select the Edit button in Body, after setting up the email output via the DW button.)

Name:<?php echo ((isset($_POST["fieldset_group_Name"]))?$_POST["fieldset_group_Name"]:"")?>
CBG Item1:<?php echo ((isset($_POST["fieldset_group_Checkbox_Group[]"]))?$_POST["fieldset_group_Checkbox_Group[]"]:"")?>
CBG Item2:<?php echo ((isset($_POST["fieldset_group_Checkbox_Group[]"]))?$_POST["fieldset_group_Checkbox_Group[]"]:"")?>
CBG Item3:<?php echo ((isset($_POST["fieldset_group_Checkbox_Group[]"]))?$_POST["fieldset_group_Checkbox_Group[]"]:"")?>

However, even though I check one (or more) of the checkboxes when I test it online, they do not show up in the email. I do see that the PHP code for all three Items is identical, which may be part of the problem.

Any thoughts on how to resolve this?