$data['query'] result to form_dropdown()

[eluser]dimaomni[/eluser]
founded:

Model:
foreach($query AS $row):
$letter[$row->letter] = &$row->letter;
$number[$row->number] = &$row->number;
endforeach;

echo form_open('index.php/adminka/studentWork');
echo form_dropdown('classroom', $letter, '1');
echo form_dropdown('classroom', $number, '1');
.....