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
代码如下:
// 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://
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';
?>
