Here is my try:
@header("Content-type: text/html; charset=utf-8");
@header("Location:/index.php");
@header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
@header("Expires: Mon, 26 Jul 1997 05:00:00 GMT"); // Date in the past
As you have seen,there is no control over "3 seconds",how to make it take effect in 3 seconds?
The easiest way to do this is to use a meta redirect or a javascript redirect. Saying as how you are serving text/html, you can echo either of these to the browser.
<meta http-equiv="refresh" content="3;URL=/newpage.php">
or
window.setTimeout(function() { window.location = '/newpage.php' }, 3000);
Edit: According to the Wikipedia page on URL redirection you can send the Refresh header directly to the browser from PHP. No clue on how well browsers support this though.
header('Refresh: 3; url=/newpage.php');
You could take advantage of the refresh meta tag, like this:
<html>
<head>
<title>redirect page</title>
<META http-equiv="refresh" content="5;URL=http://www.newurl.com">
</head>
<body bgcolor="#ffffff">
The contents you are looking for have moved.
You will be redirected to the new location automatically in 5 seconds.
</body>
</html>