tp框架加那个默认水平垂直居中就包错了，代码没有写错呀

$sheet=$PHPExcel->getActiveSheet();//获得当前活动的单元格

        $sheet->getDefaultStyle()->getAlignment()->setVertical(PHPExcel_Style_Alignment::VERTICAL_CENTER)->setHorizontal(PHPExcel_Style_Alignment::HORIZONTAL_CENTER);//设置excel文件默认水平垂直方向居中

:(

Class 'Home\Controller\PHPExcel_Style_Alignment' not found

错误位置

FILE: D:\WWW\phpexcel\Application\Home\Controller\IndexController.class.php 　LINE: 102