problem with combo box

[Ba9]

Hi
I want to create a combo box witch it contain the value for a table
from my data base then this my code :

$sqlc='select name from HRA_server;';
$resultc=mysql_query($sqlc);

$combo = PhpExt_Form_ComboBox::createComboBox("hraserv","HRA
server")
->setAllQuery($sqlc)
->setDisplayField("state")
->setTypeAhead(true)
->setMode(PhpExt_Form_ComboBox::MODE_LOCAL)
->setTriggerAction
(PhpExt_Form_ComboBox::TRIGGER_ACTION_ALL)
->setEmptyText("Select Hra server..")
->setSelectOnFocus(true);

In result I obtain the combo but it is empty.
thank you in advance for your help.