根據版主的寫法改良的：

public function renderTableFooter()
{
  $hasFilter=$this->filter!==null && $this->filterPosition===self::FILTER_POS_FOOTER;
  $hasFooter=$this->getHasFooter();
  if($hasFilter || $hasFooter)
  {
    echo "<tfoot>\n";
    if($hasFooter)
    {
      echo "<tr>\n";
      $count = 0;                
      foreach($this->columns as $column)
      {
        if($count == 0)
          $column->renderFooterCell();
        else
          $count--;			
        if($column -> getHasFooter())
          $count = $column->footerHtmlOptions['colspan'] -1;
      }              
        echo "</tr>\n";
    }
		
      if($hasFilter)
        $this->renderFilter();
        echo "</tfoot>\n";
    }
}