i added a dropdown menu by using the zen_draw_pull_down function,
$pulldown_array = array();
$pulldown_array[] = array('id' => '0', 'text' => please select);
$pulldown_array[] = array('id' => '1', 'text' => option a);
$pulldown_array[] = array('id' => '2', 'text' => option b);
zen_draw_pull_down_menu('pulldown', $pulldown_array)

after i select "option a" and confirm the form, if other input field gets an error, the value of this dropdown goes back to "please select", i want to keep the dropdown value selected (make the value goes to "option a"), what do i do?