<?phpheader("Content-type: text/html; charset=utf-8");  require('conn.php'); $id = intval($_GET['id']); $sql = "delete from lyb where ID = $id";if ($mysqli->query($sql) === true) {    echo "<meta http-equiv='Content-Type'  content='text/html; charset=utf-8'>";      echo "<script charset='utf-8' type='text/javascript'>alert('刪除成功');location.href='5-6.php';</script>"; } else {    echo "刪除失敗" . $mysqli->error;    echo  "<script>location.href='5-6.php'</script>"; } $mysqli->close();?>為何刪除成功幾個字，還是顯示為亂碼？