php导出mysql csv出现乱码是什么原因（附解决方法）

fwrite($fp, chr(0xEF) . chr(0xBB) . chr(0xBF));

function kg_export_csv($rows, $fields = [], $filename = '')
{
  $filename = $filename ?: kg_uniqid();
   
  header("Content-Type: text/csv");
  header("Content-Disposition:filename={$filename}.csv");

  $fp = fopen('php://output', 'w');

  fwrite($fp, chr(0xEF) . chr(0xBB) . chr(0xBF));

  if ($fields) fputcsv($fp, $fields);
   
  $index = 0;
  
  foreach ($rows as $row) {
 　　if ($index == 1000) {
  　$index = 0;
 　　ob_flush();
  　flush();
  }
  $index++;
  fputcsv($fp, $row);
}