www.php.cn,php强制用户转向www域名

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

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