<?php
/* 
  determine which language out of an available set the user prefers most
  
  $available_languages        array with language-tag-strings (must be lowercase) that are available
  $http_accept_language    a HTTP_ACCEPT_LANGUAGE string (read from $_SERVER['HTTP_ACCEPT_LANGUAGE'] if left out)
*/
function prefered_language ($available_languages,$http_accept_language="auto") {
    // if $http_accept_language was left out, read it from the HTTP-Header
    if ($http_accept_language == "auto") $http_accept_language = $_SERVER['HTTP_ACCEPT_LANGUAGE'];

    // standard  for HTTP_ACCEPT_LANGUAGE is defined under 
    // http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4
    // pattern to find is therefore something like this:
    //    1#( language-range [ ";" "q" "=" qvalue ] )
    // where:
    //    language-range  = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )
    //    qvalue         = ( "0" [ "." 0*3DIGIT ] )
    //            | ( "1" [ "." 0*3("0") ] )
    preg_match_all("/([[:alpha:]]{1,8})(-([[:alpha:]|-]{1,8}))?" . 
                   "(\s*;\s*q\s*=\s*(1\.0{0,3}|0\.\d{0,3}))?\s*(,|$)/i", 
                   $http_accept_language, $hits, PREG_SET_ORDER);

    // default language (in case of no hits) is the first in the array
    $bestlang = $available_languages[0];
    $bestqval = 0;

    foreach ($hits as $arr) {
        // read data from the array of this hit
        $langprefix = strtolower ($arr[1]);
        if (!empty($arr[3])) {
            $langrange = strtolower ($arr[3]);
            $language = $langprefix . "-" . $langrange;
        }
        else $language = $langprefix;
        $qvalue = 1.0;
        if (!empty($arr[5])) $qvalue = floatval($arr[5]);
      
        // find q-maximal language  
        if (in_array($language,$available_languages) && ($qvalue > $bestqval)) {
            $bestlang = $language;
            $bestqval = $qvalue;
        }
        // if no direct hit, try the prefix only but decrease q-value by 10% (as http_negotiate_language does)
        else if (in_array($langprefix,$available_languages) && (($qvalue*0.9) > $bestqval)) {
            $bestlang = $langprefix;
            $bestqval = $qvalue*0.9;
        }
    }
    return $bestlang;
}
?>

<?php
/* 
  determine which language out of an available set the user prefers most
  
  $available_languages        array with language-tag-strings (must be lowercase) that are available
  $http_accept_language    a HTTP_ACCEPT_LANGUAGE string (read from $_SERVER['HTTP_ACCEPT_LANGUAGE'] if left out)
*/
function prefered_language ($available_languages,$http_accept_language="auto") {
    // if $http_accept_language was left out, read it from the HTTP-Header
    if ($http_accept_language == "auto") $http_accept_language = $_SERVER['HTTP_ACCEPT_LANGUAGE'];

    // standard  for HTTP_ACCEPT_LANGUAGE is defined under 
    // http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4
    // pattern to find is therefore something like this:
    //    1#( language-range [ ";" "q" "=" qvalue ] )
    // where:
    //    language-range  = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )
    //    qvalue         = ( "0" [ "." 0*3DIGIT ] )
    //            | ( "1" [ "." 0*3("0") ] )
    preg_match_all("/([[:alpha:]]{1,8})(-([[:alpha:]|-]{1,8}))?" . 
                   "(\s*;\s*q\s*=\s*(1\.0{0,3}|0\.\d{0,3}))?\s*(,|$)/i", 
                   $http_accept_language, $hits, PREG_SET_ORDER);

    // default language (in case of no hits) is the first in the array
    $bestlang = $available_languages[0];
    $bestqval = 0;

    foreach ($hits as $arr) {
        // read data from the array of this hit
        $langprefix = strtolower ($arr[1]);
        if (!empty($arr[3])) {
            $langrange = strtolower ($arr[3]);
            $language = $langprefix . "-" . $langrange;
        }
        else $language = $langprefix;
        $qvalue = 1.0;
        if (!empty($arr[5])) $qvalue = floatval($arr[5]);
      
        // find q-maximal language  
        if (in_array($language,$available_languages) && ($qvalue > $bestqval)) {
            $bestlang = $language;
            $bestqval = $qvalue;
        }
        // if no direct hit, try the prefix only but decrease q-value by 10% (as http_negotiate_language does)
        else if (in_array($languageprefix,$available_languages) && (($qvalue*0.9) > $bestqval)) {
            $bestlang = $languageprefix;
            $bestqval = $qvalue*0.9;
        }
    }
    return $bestlang;
}
?>

http://de2.php.net/manual/en/function.http-negotiate-language.php#

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