Just a couple of notes.
1) don't use a '$' in front of the variables you are sending
to Flash.
"$comboData1" should be "comboData1"
2) Not sure about using multipl "echo" statements. I never
have but that doesn't mean you can't.
3) Try something straightforward first, like:
echo 'comboData1=this is data 1';
If that works then move up to trying the variables.
4) The last thing to note is that your PHP variables are
surrounded by quotes.
"$dataForCombobox_1" should be $dataForCombobox_1
Hope these help.
Tim