PHP header 刷新警告

Question

我有这个代码:

<?php
session_start();
echo "".$_SESSION['eventnum']."";
$urlRefresh = "testremot.php";
header("Refresh: 5; URL=\"" . $urlRefresh . "\"");
?>

但是 header 不起作用，并且当我尝试运行此代码时出现此警告:

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\remot\testremot.php:3) in C:\xampp\htdocs\remot\testremot.php on line 5**

你能帮我吗？

Answer 1

好的，让我们看看第 3 行中有什么内容:

echo "".$_SESSION['eventnum']."";

显然，您正在此行中生成输出 (echo)，并且此行出现在您调用 header 之前。
将其移至 header 下方:

session_start();
$urlRefresh = "testremot.php";
header("Refresh: 5; URL=\"" . $urlRefresh . "\"");
echo "".$_SESSION['eventnum']."";

---

但请注意(来自 Wikipedia ):

The W3C's Web Content Accessibility Guidelines (7.4) discourage the creation of auto-refreshing pages, since most web browsers do not allow the user to disable or control the refresh rate.