Let me clarify this for myself: You have a list of checkboxes
<input type="checkbox" value="PersonA">PersonA<br>
<input type="checkbox" value="PersonB">PersonB<br>
<input type="checkbox" value="PersonC">PersonC<br>
<input type="checkbox" value="PersonD">PersonD<br>
<input type="checkbox" value="PersonE">PersonE<br>
...and you want the values of all the checked checkboxes to be available to the script processing the form in a single array called $to?
In that case consider naming the checkboxes thus:
<input type="checkbox" name="to[]" value="PersonA">PersonA<br>
<input type="checkbox" name="to[]" value="PersonB">PersonB<br>
<input type="checkbox" name="to[]" value="PersonC">PersonC<br>
<input type="checkbox" name="to[]" value="PersonD">PersonD<br>
<input type="checkbox" name="to[]" value="PersonE">PersonE<br>
Example:
[ ]PersonA
[X]PersonB
[ ]PersonC
[ ]PersonD
[X]PersonE
would result in the array
$to=array('PersonB','PersonE');
being set in the called script.
Is this what you're looking for?