Question

I have a multi-languagepage, I want to detect client browser’s language then make a 301 home page or other thing. but I am not sure which way is better for seo. I do not know web spider like which one? Or other way?

<?php 
$LG=$_SERVER['HTTP_ACCEPT_LANGUAGE']; 
if (preg_match('/^[zZ][hH]/', $LG)) {
header("HTTP/1.1 301 Moved Permanently");
header("Location: http://mydomain.com/cn/");
exit();} //jump to chinese version
else { 
header("HTTP/1.1 301 Moved Permanently");
header("Location: http://mydomain.com/en/");
exit();} //jump to english version
?>

OR

<?php 
$LG=$_SERVER['HTTP_ACCEPT_LANGUAGE']; 
if (preg_match('/^[zZ][hH]/', $LG)) {
include ("http://mydomain.com/cn/");
} //include chinese version
else { 
header("HTTP/1.1 301 Moved Permanently");
include ("http://mydomain.com/en/");
} //include english version
?>

OR other way? Thanks.

Answer 1

As you already assume in your question, you need to parse the Accept-Language^HTTP/1.1 header, which is available in PHP in $_SERVER['HTTP_ACCEPT_LANGUAGE']. This first needs to be parsed into a structure you can better deal within PHP, like an array:

/**
 * Convert Accept Language to sorted PHP array
 * 
 * Related HTTP Specs:
 *   <http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4>
 *   <http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.9>
 *
 * @param string $accept header value
 * @return array ([language-range] => qvalue, ...)
 */
function http_accept_language_array($accept = NULL)
{
    if (!$accept && isset($_SERVER['HTTP_ACCEPT_LANGUAGE']))
        $accept = $_SERVER['HTTP_ACCEPT_LANGUAGE'];
    $accept = (string) $accept;

    $pattern = '/([a-z]{1,8}(-[a-z]{1,8})?)(;q=([01](?:\.[0-9]{0,3})?))?(?=$|,[ ]*)/i';
    preg_match_all($pattern, $accept, $matches);

    $array = array();
    if (count($matches[1]))
    {
        list(, $ranges,,, $qvals) = $matches;
        # normalize ranges
        foreach ($ranges as &$range)
            $range = strtolower($range);
        unset ($range);
        # set default qvalue 1
        foreach ($qvals as &$qval)
            if ('' === $qval) $qval = '1';
        unset ($qval);        
        $array = array_combine($ranges, $qvals);
        arsort($array, SORT_NUMERIC);
    }
    return $array;
}

Which for da, en-gb;q=0.8, en;q=0.7 will return:

array(3) {
  ["da"]    => string(1) "1"
  ["en-gb"] => string(3) "0.8"
  ["en"]    => string(3) "0.7"
}

You then need to parse this sorted array to find your first match, setting your preference with the en default value:

$lang = 'en';
foreach (http_accept_language_array() as $range => $qvalue)
{
    if (preg_match('/^zh[$-]/', $range))
    {
        $lang = 'cn';
        break;
    }
}

Finally you can do the redirect based on $lang (or the include or whatever):

header("HTTP/1.1 301 Moved Permanently");
header("Location: http://mydomain.com/$lang/");

If you’re looking for a ready-made library to deal with this, one existing solution is the Symfony’s HttpFoundation\Request or in PEAR there is HTTP::negotiateLanguage.

The PHP intl extension has another low-level function that is related, however it’s doesn’t offer an array but a single value: locale_accept_from_http

Another general resource for more HTTP related information is Advanced handling of HTTP requests in PHP.