PHP只是以HTTP协议将HTML文档的标头送到浏览器，告诉浏览器具体怎么处理这个页面，至于传送的内容则需要熟悉一下HTTP协议了，与PHP无关

在php语言中，header()这个函数很有用的，尤其在用到ajax时候，他会帮你解决一些意想不到的问题。下面是header的一些详细讲解。希望对phper有帮助

 
<?php 
// fix 404 pages: 
header('HTTP/1.1 200 OK'); 
// set 404 header: 
header('HTTP/1.1 404 Not Found'); 
// set Moved Permanently header (good for redrictions) 
// use with location header 
header('HTTP/1.1 301 Moved Permanently'); 
// redirect to a new location: 
header('Location: http://www.example.org/'); 
// redrict with delay: 
header('Refresh: 10; url=http://www.example.org/'); 
print 'You will be redirected in 10 seconds'; 
// you could also use the HTML syntax:// <meta http-equiv="refresh" content="10;http://www.example.org/ /> 
// override X-Powered-By: PHP: 
header('X-Powered-By: PHP/4.4.0'); 
header('X-Powered-By: Brain/0.6b'); 
// content language (en = English) 
header('Content-language: en'); 
// last modified (good for caching) 
$time = time() C 60; // or filemtime($fn), etc 
header('Last-Modified: '.gmdate('D, d M Y H:i:s', $time).' GMT'); 
// header for telling the browser that the content 
// did not get changed 
header('HTTP/1.1 304 Not Modified'); 
// set content length (good for caching): 
header('Content-Length: 1234'); 
// Headers for an download: 
header('Content-Type: application/octet-stream'); 
header('Content-Disposition: attachment; filename="example.zip"'); 
header('Content-Transfer-Encoding: binary'); 
// load the file to send:readfile('example.zip'); 
// Disable caching of the current document: 
header('Cache-Control: no-cache, no-store, max-age=0, must-revalidate'); 
header('Expires: Mon, 26 Jul 1997 05:00:00 GMT'); 
// Date in the pastheader('Pragma: no-cache'); 
// set content type: 
header('Content-Type: text/html; charset=iso-8859-1'); 
header('Content-Type: text/html; charset=utf-8'); 
header('Content-Type: text/plain'); 
// plain text file 
header('Content-Type: image/jpeg'); 
// JPG picture 
header('Content-Type: application/zip'); 
// ZIP file 
header('Content-Type: application/pdf'); 
// PDF file 
header('Content-Type: audio/mpeg'); 
// Audio MPEG (MP3,…) file 
header('Content-Type: application/x-shockwave-flash'); 
// Flash animation// show sign in box 
header('HTTP/1.1 401 Unauthorized'); 
header('WWW-Authenticate: Basic realm="Top Secret"'); 
print 'Text that will be displayed if the user hits cancel or '; 
print 'enters wrong login data'; 
?>