Something

case 'search_block_form':
      $project_type_tids = array(
        '' => t('All'),
        6 => t('6'),
        7 => t('7'),
        8 => t('8'),
      );
      $form['advanced'] = array('#weight' => -1);
      $form['advanced']['category'] = array(
        '#type' => 'select',
        '#title' => t('Search in'),
        '#options' => $project_type_tids,
      );
      
      $form['basic']['inline']['processed_keys'] = array('#type' => 'value', '#value' => array());
        
      $form['#validate'] = array(
        'bigideas_search_validate' => array(),
        'node_search_validate' => array(),
      );
      $form['#submit'] = array(
        'search_form_submit' => array(),
      );
      break;