CC6 Dynamic Dropdown for filtering table

Wonder if anyone could help.
​
We are using CC6 to display a table, along with 2 dropdown filters. The options within the 2nd dropdown filter depends on what is chosen for the 1st dropdown filter. In Chronoforms6, this is achieved by using {var:somephpcode} under the 2nd dropdown's options. However, doing the same in CC6 seems to be much more difficult.
​
Tried using the exact same {var:somephpcode} under dropdown's options in CC6 doesn't seem to work. Is there any way to achieve this?
​

$options = [];
switch($this->data('course')){
 case '1':
   $options = ['A' => 'A'];
   break;
 case '2':
   $options = ['B' => 'B' , 'C' => 'C'];
   break;
 case '3':
   $options = ['D' => 'D'];
   break;
 default:
   $options = ['N/A' => 'Please select one'];
}
return $options;

The above works when put into a [php] in CF. When put into CCv6, it does not output anything.[/php]

$options = '';
switch($this->data('course')){
 case '1':
   $options = 'A';
   break;
 case '2':
   $options = 'B , C';
   break;
 case '3':
   $options = 'D';
   break;
 default:
   $options = 'Please select one';
}
echo $options;

When output as an echo, it correctly shows up within the dropdown's options. However, we can't make display multiple options. What format does the {var:} has to output into the dropdown's options? Array doesn't work.
​
[[> later: edited to add a missing ; <]]

Thank you for this tread, there is only an error in php code, missing a ";"
This is for me the correct code:
​
switch($this->data('course')){
case '1':
$options = ['A' => 'A'];
break;
case '2':
$options = ['B' => 'B', 'C' => 'C'];
break;
default:
$options = ['N/A' => 'Please select one'];
}
return $options;