Php Excel上传给我空白表格

我正在使用PHPExcel将数据库中的数据上传到excel中。下载正确，只是它为我返回了一个空的excel表，我似乎不明白问题的真正原因。如果你能帮助我，我会很高兴的。在下面找到我上传的代码片段

 <?php
include("connection/db.php");
$uploadedStatus = 0;
$msg="";
include 'Classes/PHPExcel/IOFactory.php';
if(isset($_POST['submit'])){
    $schId=$_POST['schId'];
    $program=$_POST['program'];

  $objPHPExcel = new PHPExcel();
  if($program=="All"){
      echo $query1 = "SELECT * FROM studentrec WHERE schId='$schId'";
      }
      else{
          $query1 = "SELECT * FROM studentrec WHERE schId='$schId' AND program='$program'";
          }

  $exec1 = mysqli_query($conn,$query1) or die ("Error in Query1".mysqli_error());
  $serialnumber=0;
  //Set header with temp array
  $tmparray =array("Student ID","First Name","Last Name");
  //take new main array and set header array in it.
  $sheet =array($tmparray);

  while ($res1 = mysqli_fetch_array($exec1))
  {
    $tmparray =array();
    $serialnumber = $serialnumber + 1;
    array_push($tmparray,$serialnumber);
    $employeelogin = $res1['stdId'];
    array_push($tmparray,$employeelogin);
    $employeename = $res1['fst_name'];
    array_push($tmparray,$employeename);   
    $lst_name = $res1['lst_name'];
    array_push($tmparray,$lst_name); 
    array_push($sheet,$tmparray);
  }
   header('Content-type: application/vnd.ms-excel');
   header('Content-Disposition: attachment; filename="name.xlsx"');
  $worksheet = $objPHPExcel->getActiveSheet();
  foreach($sheet as $row => $columns) {
    foreach($columns as $column => $data) {
        $worksheet->setCellValueByColumnAndRow($column, $row + 1, $data);
    }
  }

  //make first row bold
  $objPHPExcel->getActiveSheet()->getStyle("A1:I1")->getFont()->setBold(true);
  $objPHPExcel->setActiveSheetIndex(0);
  $objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
  $objWriter->save(str_replace('.php', '.xlsx', __FILE__));
  }
?>

下载什么？您正在将文件保存到服务器上的文件，而不是将文件发送到浏览器是的，我正在将文件保存到服务器上的文件。但是这张纸是空白的。问题可能是什么？那你为什么要谈论上传和下载？你如何查看服务器上的文件？我打开了保存在服务器上的文件，工作表是空的。然后检查日志，进行一些基本调试，看看为什么它甚至不包含这些标题