本文主要介绍了php强制用户转向www域名的方法，可实现模拟301重定向的功能，并且针对无法head重定向的情况输出链接。本文实例讲述了php强制用户转向www域名的方法。分享给大家供大家参考。
具体分析如下：
有时候网站的www域名和非www域名都能访问网站，但是这样不利于搜索引擎的收录，会分散网页的权重，所以希望用户访问非www的域名时通过301永久重定向到www域名，例如用户访问php.cn会直接转向www.php.cn，本php代码考虑了无法通过head重定向的情况，会在页面上输出链接，让用户点击。
// Install info.:
// Copy and paste these lines into your default index.php or
// the file that get's called if a visitor comes on your
// website...
// read the host from the server environment
$host = $_SERVER["HTTP_HOST"];
// fix host name - we never now... ;-)
$host = strtolower($host);
$host = trim($host);
// This is important:
// Webbrowsers like Firefox are doing their request without
// the port number like "www.php.cn" but some other
// applications send host names like "www.php.cn:80"
$host = str_replace(':80', '', $host);
$host = trim($host);
// if the host is not starting with www. redirect the
// user to the same URL but with www :-)
if ($host != 'www.php.cn'){
// You an also change the "!=" to "==", if you want to force
// the user to use the domain name without the www.
// send status header, so that search engines or other services
// detect that this is a permanent redirect and not a temporary
header('HTTP/1.1 301 Moved Permanently');
// read the URL the user requested:
$url = isset($_SERVER["REQUEST_URI"]) ? $_SERVER["REQUEST_URI"] : '';
// redirect the user to the new destination:
header('Location: http://www.php.cn' . $url);
// Convert "special" chars -- cause we never now... ;-)
$url = htmlspecialchars($url);
// "fallback" link, if the browser is not supporting header redirects
print 'Please click here';
// stop the script execution here
exit;
}
// If the domain is www.php.cn then go on with your PHP code
// of with your website...
// BTW: You need to replace php.cn trough your own domain :-D相关推荐：
cqcms通用企业建站(PC+wap)2.9
下载
cqcms通用企业建站介绍 苍穹企业网站管理系统(CQCMS)软件是国产PHP网站内容管理系统：CQcms内容管理系统 ，它将成为您轻松建站的利器。模板全部使用文件形式保存，对用户设计模板、网站升级转移均提供很大的便利，健壮的模板标签为站长DIY自己的网站提供了强有力的支持。MVC框架，自定义标签，模板文件修改非常方便，PC+WAP响应式布局，一个域名，自动识别终端，一个后台同时管理PC和wap。
立即学习“PHP免费学习笔记（深入）”；
