Drupal theme_table order by field 不能正常使用

Drupal version 6.30


以下代码ＡＰＩ地址
https://api.drupal.org/api/drupal/includes!tablesort.inc/function/tablesort_header/6
/**
 * Format a column header.
 *
 * If the cell in question is the column header for the current sort criterion,
 * it gets special formatting. All possible sort criteria become links.
 *
 * @param $cell
 *   The cell to format.
 * @param $header
 *   An array of column headers in the format described in theme_table().
 * @param $ts
 *   The current table sort context as returned from tablesort_init().
 * @return
 *   A properly formatted cell, ready for _theme_table_cell().
 */
function tablesort_header($cell, $header, $ts) {
  // Special formatting for the currently sorted column header.
  if (is_array($cell) && isset($cell['field'])) {
    $title = t('sort by @s', array('@s' => $cell['data']));
    if ($cell['data'] == $ts['name']) {
      $ts['sort'] = (($ts['sort'] == 'asc') ? 'desc' : 'asc');
      if (isset($cell['class'])) {
        $cell['class'] .= ' active';
      }
      else {
        $cell['class'] = 'active';
      }
      $image = theme('tablesort_indicator', $ts['sort']);
    }
    else {
      // If the user clicks a different header, we want to sort ascending initially.
      $ts['sort'] = 'asc';
      $image = '';
    }

    if (!empty($ts['query_string'])) {
      $ts['query_string'] = '&'. $ts['query_string'];
    }
    $cell['data'] = l($cell['data'] . $image, $_GET['q'], array('attributes' => array('title' => $title), 'query' => 'sort='. $ts['sort'] .'&order='. urlencode($cell['data']) . $ts['query_string'], 'html' => TRUE));

    unset($cell['field'], $cell['sort']);
  }
  return $cell;
}


这里的   
$cell['data'] = l($cell['data'] . $image, $_GET['q'], array('attributes' => array('title' => $title), 'query' => 'sort='. $ts['sort'] .'&order='. urlencode($cell['data']) . $ts['query_string'], 'html' => TRUE));

'&order='. urlencode($cell['data']) . $ts['query_string']

$cell['data']是ｈｅａｄｅｒ里面的ｄａｔａ，而不是ｆｉｅｌｄ。


不改核心代码的情况下解决办法
$order = trim($_GET['order']) ? trim($_GET['order']) : 'n.a';
$sort = trim($_GET['sort']) ? trim($_GET['sort']) : 'asc';

$header = array(
    array('data' => t('A1'), 'field' => 'n.a', 'sort' => 'asc'),
    array('data' => t('A2'), 'field' => 'n.b', 'sort' => 'asc'),
    array('data' => t('A3'), 'field' => 'n.c', 'sort' => 'asc'),
    array('data' => t('A4'), 'field' => 'n.d', 'sort' => 'asc'),
  );
  foreach ($header as $item) {
    if ($order == $item['data'] || $order == $item['field']) {
      $order = $item['field'];
    }
  }
  $sql .= " ORDER BY %s %s  ";
  $args[] = $order;
  $args[] = $sort;