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jb51.cc会直接转向www.jb51.cc，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。
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// 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.jb51.cc" but some other
// applications send host names like "www.jb51.cc: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.jb51.cc'){
// 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: //www.jb51.cc' . $url);
// Convert "special" chars -- cause we never Now... ;-)
$url = htmlspecialchars($url);
// "fallback" link,if the browser is not supporting header redirects
print '';
// stop the script execution here
exit;
}
// If the domain is www.jb51.cc then go on with your PHP code
// of with your website...
// BTW: You need to replace jb51.cc trough your own domain :-D
希望本文所述对大家的PHP程序设计有所帮助。
