Detect Browser Language in PHP

Question

I use the following PHP script as index for my website.

This script should include a specific page depending on the browser\'s language (automatically detected).

Answer 1

why dont you keep it simple and clean

<?php
    $lang = substr($_SERVER['HTTP_ACCEPT_LANGUAGE'], 0, 2);
    $acceptLang = ['fr', 'it', 'en']; 
    $lang = in_array($lang, $acceptLang) ? $lang : 'en';
    require_once "index_{$lang}.php"; 

?>

Answer 2

The problem with the selected answer above is that the user may have their first choice set as a language that's not in the case structure, but one of their other language choices are set. You should loop until you find a match.

This is a super simple solution that works better. Browsers return the languages in order of preference, so that simplifies the problem. While the language designator can be more than two characters (e.g. - "EN-US"), typically the first two are sufficient. In the following code example I'm looking for a match from a list of known languages my program is aware of.

$known_langs = array('en','fr','de','es');
$user_pref_langs = explode(',', $_SERVER['HTTP_ACCEPT_LANGUAGE']);

foreach($user_pref_langs as $idx => $lang) {
    $lang = substr($lang, 0, 2);
    if (in_array($lang, $known_langs)) {
        echo "Preferred language is $lang";
        break;
    }
}

I hope you find this a quick and simple solution that you can easily use in your code. I've been using this in production for quite a while.

Answer 3

Accept-Language is a list of weighted values (see q parameter). That means just looking at the first language does not mean it’s also the most preferred; in fact, a q value of 0 means not acceptable at all.

So instead of just looking at the first language, parse the list of accepted languages and available languages and find the best match:

// parse list of comma separated language tags and sort it by the quality value
function parseLanguageList($languageList) {
    if (is_null($languageList)) {
        if (!isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
            return array();
        }
        $languageList = $_SERVER['HTTP_ACCEPT_LANGUAGE'];
    }
    $languages = array();
    $languageRanges = explode(',', trim($languageList));
    foreach ($languageRanges as $languageRange) {
        if (preg_match('/(\*|[a-zA-Z0-9]{1,8}(?:-[a-zA-Z0-9]{1,8})*)(?:\s*;\s*q\s*=\s*(0(?:\.\d{0,3})|1(?:\.0{0,3})))?/', trim($languageRange), $match)) {
            if (!isset($match[2])) {
                $match[2] = '1.0';
            } else {
                $match[2] = (string) floatval($match[2]);
            }
            if (!isset($languages[$match[2]])) {
                $languages[$match[2]] = array();
            }
            $languages[$match[2]][] = strtolower($match[1]);
        }
    }
    krsort($languages);
    return $languages;
}

// compare two parsed arrays of language tags and find the matches
function findMatches($accepted, $available) {
    $matches = array();
    $any = false;
    foreach ($accepted as $acceptedQuality => $acceptedValues) {
        $acceptedQuality = floatval($acceptedQuality);
        if ($acceptedQuality === 0.0) continue;
        foreach ($available as $availableQuality => $availableValues) {
            $availableQuality = floatval($availableQuality);
            if ($availableQuality === 0.0) continue;
            foreach ($acceptedValues as $acceptedValue) {
                if ($acceptedValue === '*') {
                    $any = true;
                }
                foreach ($availableValues as $availableValue) {
                    $matchingGrade = matchLanguage($acceptedValue, $availableValue);
                    if ($matchingGrade > 0) {
                        $q = (string) ($acceptedQuality * $availableQuality * $matchingGrade);
                        if (!isset($matches[$q])) {
                            $matches[$q] = array();
                        }
                        if (!in_array($availableValue, $matches[$q])) {
                            $matches[$q][] = $availableValue;
                        }
                    }
                }
            }
        }
    }
    if (count($matches) === 0 && $any) {
        $matches = $available;
    }
    krsort($matches);
    return $matches;
}

// compare two language tags and distinguish the degree of matching
function matchLanguage($a, $b) {
    $a = explode('-', $a);
    $b = explode('-', $b);
    for ($i=0, $n=min(count($a), count($b)); $i<$n; $i++) {
        if ($a[$i] !== $b[$i]) break;
    }
    return $i === 0 ? 0 : (float) $i / count($a);
}

$accepted = parseLanguageList($_SERVER['HTTP_ACCEPT_LANGUAGE']);
var_dump($accepted);
$available = parseLanguageList('en, fr, it');
var_dump($available);
$matches = findMatches($accepted, $available);
var_dump($matches);

If findMatches returns an empty array, no match was found and you can fall back on the default language.

Answer 4

The existing answers are a little too verbose so I created this smaller, auto-matching version.

function prefered_language(array $available_languages, $http_accept_language) {

    $available_languages = array_flip($available_languages);

    $langs;
    preg_match_all('~([\w-]+)(?:[^,\d]+([\d.]+))?~', strtolower($http_accept_language), $matches, PREG_SET_ORDER);
    foreach($matches as $match) {

        list($a, $b) = explode('-', $match[1]) + array('', '');
        $value = isset($match[2]) ? (float) $match[2] : 1.0;

        if(isset($available_languages[$match[1]])) {
            $langs[$match[1]] = $value;
            continue;
        }

        if(isset($available_languages[$a])) {
            $langs[$a] = $value - 0.1;
        }

    }
    arsort($langs);

    return $langs;
}

And the sample usage:

//$_SERVER["HTTP_ACCEPT_LANGUAGE"] = 'en-us,en;q=0.8,es-cl;q=0.5,zh-cn;q=0.3';

// Languages we support
$available_languages = array("en", "zh-cn", "es");

$langs = prefered_language($available_languages, $_SERVER["HTTP_ACCEPT_LANGUAGE"]);

/* Result
Array
(
    [en] => 0.8
    [es] => 0.4
    [zh-cn] => 0.3
)*/

Full gist source here

Answer 5

All of the above with fallback to 'en':

$lang = substr(explode(',',$_SERVER['HTTP_ACCEPT_LANGUAGE'])[0],0,2)?:'en';

...or with default language fallback and known language array:

function lang( $l = ['en'], $u ){
    return $l[
        array_keys(
            $l,
            substr(
                explode(
                    ',',
                    $u ?: $_SERVER['HTTP_ACCEPT_LANGUAGE']
                )[0],
                0,
                2
            )
        )[0]
    ] ?: $l[0];
}

One Line:

function lang($l=['en'],$u){return $l[array_keys($l,substr(explode(',',$u?:$_SERVER['HTTP_ACCEPT_LANGUAGE'])[0],0,2))[0]]?:$l[0];}

Examples:

// first known lang is always default
$_SERVER['HTTP_ACCEPT_LANGUAGE'] = 'en-us';
lang(['de']); // 'de'
lang(['de','en']); // 'en'

// manual set accept-language
lang(['de'],'en-us'); // 'de'
lang(['de'],'de-de, en-us'); // 'de'
lang(['en','fr'],'de-de, en-us'); // 'en'
lang(['en','fr'],'fr-fr, en-us'); // 'fr'
lang(['de','en'],'fr-fr, en-us'); // 'de'

Answer 6

Unfortunately, none of the answers to this question takes into account some valid HTTP_ACCEPT_LANGUAGE such as:

• q=0.8,en-US;q=0.5,en;q=0.3: having the q priority value at first place.
• ZH-CN: old browsers that capitalise (wrongly) the whole langcode.
• *: that basically say "serve whatever language you have".

After a comprehensive test with thousands of different Accept-Languages in my server, I ended up having this language detection method:

define('SUPPORTED_LANGUAGES', ['en', 'es']);

function detect_language() {
    foreach (preg_split('/[;,]/', $_SERVER['HTTP_ACCEPT_LANGUAGE']) as $sub) {
        if (substr($sub, 0, 2) == 'q=') continue;
        if (strpos($sub, '-') !== false) $sub = explode('-', $sub)[0];
        if (in_array(strtolower($sub), SUPPORTED_LANGUAGES)) return $sub;
    }
    return 'en';
}