ahah helper populate dependent dropdown

Question

I am using the ahah helper as I couldn't seem to get my dropdown lists to depend on each other anyother way in Drupal 6. Below is my code, I can hard code the changes so that the second dropdown populates with the correct values. However when I select a value from dropdown one An error occurred. /drupal1/?q=ahah_helper/dependent_select (no information available).

There is no error in my httpd log. All i have changed is, added a DB connection, two queries to populate $grouplist and $sitelist with the latter referencing the selected value from list one for the WHERE clause in the query. I am still passing a ID number which refers to a value. See directly below for the previous code that worked in the example. I have taken the $select1_selected and used that within the query that populates dropdown2.

Dropdown one options = '#options' => array( 1=> 'USA', 2 => 'German'),

Dropdown two options =

 if ( $select1_selected == 1 ) {
    $select2_options['11'] = 'GM';
    $select2_options['12'] = 'Ford';
} else if ( $select1_selected == 2 ) {
    $select2_options['21'] = 'VW';
    $select2_options['22'] = 'Audi';
}   

My Code:

    function ahahdrop_menu(){
        $items = array();
        $items['ahahdrop'] = array(
        'title' => 'Ahah Drop menu',
        'type' => MENU_NORMAL_ITEM,
        'access arguments' => array('access ahahdrop'),
        'page callback' => 'drupal_get_form',
        'page arguments' => array ('ahahdrop_form'),
    );
return $items;
 }

    function ahahdrop_form( $form_state ) {
        $form = array();
    // this is standard method for register ahah helper for current form   
        ahah_helper_register($form, $form_state);

    // we are building fieldset 
        $form['dependent_select'] =
        array(
         '#type'   => 'fieldset',
         '#title'  => t('Dependent Select '),
         '#prefix' => '<div id="dependent-select-wrapper">',  // specify wrapper element id
         '#suffix' => '</div>',
         '#tree'   => TRUE,  // this should be TRUE
         );   

    // provide default option for select one
        $select1_selected = 11;

    // $form_state['storage'], contains ahah submitted values
        if ( isset($form_state['storage']['dependent_select']['select1']) ) {
    // get 'select1' selected option
        $select1_selected =  $form_state['storage']['dependent_select']['select1'] ;
} 

 try {  $conn = new PDO("pgsql:host=localhost port=5432 dbname=riverflies_gis", "opengeo", "opengeo");
        echo "Connected";
            echo "<br>";
    }
        catch(PDOException $e) {
            echo $e->getMessage();
        }

        $stmt2 = $conn->prepare("SELECT group_id, rmigroupname FROM rmi_group_tbl ");
            if ($stmt2->execute()) {
                $stmt2->setFetchMode(PDO::FETCH_OBJ);
                    $grouplist = array();
                        foreach ($stmt2 as $row) {
                        $grouplist[$row->group_id] = $row->rmigroupname;
            }
    }   

        $stmt3 = $conn->prepare("SELECT site_id, sitename, group_id FROM sites_tbl WHERE group_id = $select1_selected ");
            if ($stmt3->execute()) {
                $stmt3->setFetchMode(PDO::FETCH_OBJ);
                    $siteslist = array();
                        foreach ($stmt3 as $row) {
                        $siteslist[$row->site_id] = $row->sitename;
            }
    }

    $form['dependent_select']['select1'] =
        array(
         '#type'    => 'select',
         '#title'   => t('Select 1'),
         '#options' => $grouplist,
         '#default_value' => array( $select1_selected ),
         // specify ahah event
         '#ahah' => array(
                        'event'   => 'change',  //  this is onchange event of select
                        'path'    => ahah_helper_path(array('dependent_select')),
                        // provide temporary path
                        // no need to register it through hook_menu
                        'wrapper' => 'dependent-select-wrapper',
                        // provide the wrapper of element
                        // here we have given the id of fieldset
                        ),
          );

    $form['dependent_select']['select2'] =
        array(
         '#type'    => 'select',
         '#title'   => t('Select 2'),
         '#options' =>  $siteslist // set dynamic options        
         );

    $form['submit'] =
        array( '#type'  => 'submit',
           '#value' => t('Save')
           );

    return $form;
    }

Answer 1

See the ahah drop down examples in drupal examples module