Drupal 7, Problemer med Hierarkisk dropdown lists

Hej jeg har nedenstående formular med 2 dropwornlist i. Den anden dropdown skal udfyldes efter vi har valgt en værdi fra den første dropdown. Men den ser ikke ud til at køre koden.
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function find_tryk_filter_form($form, &$form_state) {
        // Now the fun begins.  For this simple example,
        // we will only provide two form elements.
        // 1. an input for the friend's email address
        // 2. a submit button
        // You can add as much or as little to this form as
        // needed.  See the forms api for all possible elements.
       
        //Query DB for Rows

        $results = db_query("SELECT DISTINCT ttd.tid,ttd.name FROM taxonomy_term_data AS ttd JOIN field_data_field_producent AS fp
        ON ttd.tid = fp.field_producent_tid JOIN field_data_field_branche ffb ON fp.entity_id = ffb.entity_id JOIN node 
        ON node.nid = ffb.field_branche_target_id
        WHERE node.title = 'Trykluft'");
   
    $options = array();   
        foreach ($results as $result) {
      $options[$result->tid] = $result->name;
}
       
        //Default value for 1st select
  $selected = isset($form_state['values']['find_tryk_filter']['level1']) ? $form_state['values']['find_tryk_filter']['level1'] : key($options);   
 
 
               
        $form['find_tryk_filter']['level1'] = array(
                // #type tells drupal what kind of element to build
                                             
                //'#default_value' => 34,
                            '#type' => 'select',
                            '#options' => $options,
                            '#ajax' => array(
                            //Call function that rebuilt select2 field
                            'event' => 'change',
                          'callback' => 'ajax_dropdown_callback',
                          'wrapper' => 'second-option',
    ),   
        );
       
        $form['find_tryk_filter']['level2'] = array(
                // #type tells drupal what kind of element to build
                                             
                //'#default_value' => 34,
                            '#type' => 'select',
                            '#options' => populateSecondDropdown($selected) ,
                            //populateSecondDropdown($selected),
                            '#default_value' => isset($form_state['values']['find_tryk_filter']['level2']) ? $form_state['values']['find_tryk_filter']['level2'] : '',    
                            '#prefix' => '<div id="dropdown-second-replace">',
                            '#suffix' => '</div>',
        );
        $form['submit'] = array(
                '#type' => 'submit',
                // #value is the text to display inside the button
                '#value' => t('Find filter element'),
        );
               
               

        return $form;
}


function ajax_dropdown_callback($form, &$form_state) {
  return $form['find_tryk_filter_level2'];
}

function populateSecondDropdown($key='')
{
    $selectedKey = array();
        $results = db_query("SELECT ttd.tid,ttd.name FROM taxonomy_term_data AS ttd
                    JOIN field_data_field_flow AS ff
                    ON ff.field_flow_tid = ttd.tid
                    JOIN field_data_field_producent AS fp
                    ON fp.entity_id = ff.entity_id
                    JOIN node
                    ON fp.entity_id = node.nid
                    WHERE fp.field_producent_tid = '".$key."'");
   
            $options = array();
       
       
            foreach ($results as $result)
            {
              $options[$result->tid] = $result->name;
            }
               
          $selectedKey[$key]  = $options;
      if(isset($selectedKey[$key]))
            {
                return $selectedKey[$key];
            }        
               
               
 
}
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