build checkbox dynamic

need to build diffrent chackboxs for each category, i try this code (just for test).

foreach($form["fields"] as &$field)
switch($field["id"])
{
case "5":
$field['inputs']=array();
$a = array( 'id' => '5.1',
'label' => 'test',
'name' => '',
);
$field['inputs'][] = $a;
break;
}

but it is not working, the array date changed but no effect on display!!

i will give an example.
i want the same form to be diffrent by variable that give the number of checkboxes.
need a way to build form checkbox dynamicly.