如何将几个选定的表导出到单个excel文件中，每个表都有一张工作表？
下面是我目前的代码。

$con = mysqli_connect("localhost","root","","test1");

if(isset($_POST["download"]))  
 {  

      header('Content-Type: text/csv; charset=windows-1257');  
      header('Content-Disposition: attachment; filename=TEST.csv');  
      $output = fopen("php://output", "w");  
      fputcsv($output, array( 'ID', 'Name','type'));  
      $query = "SELECT * from table1";  
      $result = mysqli_query($con, $query);  
      while($row = mysqli_fetch_assoc($result))  
      {  
           fputcsv($output, $row);  
      }  
      fclose($output);  
 }