$data[version_id_dc] is not the correct way to refer to a posted form element value.
If the forms method is set to post, the proper code to get the value would be:
$_POST['elementName']
For a checkbox, the value that is posted will be the value added to the value attribute:
<input name="checkbox" type="checkbox" id="checkbox" value="my value" />
to check if this checkbox was checked, the code would be:
if(isset($POST['checkbox']) && $POST['checkbox'] != "") {