phpexcel 使用getComment获取xls单元格中文批注为乱码

如题.

表格内容

include_once('includes/PHPExcel.php');
$uploadfile = xxx;
$type = strtolower( pathinfo($uploadfile, PATHINFO_EXTENSION) );
if ($type == 'xls' || $type == 'xlsx') {
    $objPHPExcel = PHPExcel_IOFactory::load($uploadfile)
} else if ($type == 'csv') {
    $objReader = PHPExcel_IOFactory::createReader('CSV')
        ->setDelimiter(',')
        ->setInputEncoding('GBK') //不设置将导致中文列内容返回boolean(false)或乱码
        ->setEnclosure('"')
        ->setLineEnding("\r\n")
        ->setSheetIndex(0);
    $objPHPExcel = $objReader->load($uploadfile);
}

$sheet = $objPHPExcel->getSheet(0);
$plaintext = $sheet->getComment("A1");
echo $plaintext;

$plaintext值为乱码