Identify language from the Accept-language HTTP header we got.

We perform browser accept-language parsing only if page cache is disabled, otherwise we would cache a user-specific preference.

Parameters

$languages: An array of language objects for enabled languages ordered by weight.

Return value

A valid language code on success, FALSE otherwise.

Related topics

1 call to locale_language_from_browser()

LocaleBrowserDetectionTest::testLanguageFromBrowser in modules/locale/locale.test

Unit tests for the locale_language_from_browser() function.

1 string reference to 'locale_language_from_browser'

locale_language_negotiation_info in modules/locale/locale.module

Implements hook_language_negotiation_info().

File

includes/locale.inc, line 131

Code

function locale_language_from_browser($languages) {
    if (empty($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
        return FALSE;
    }
    // The Accept-Language header contains information about the language
    // preferences configured in the user's browser / operating system.
    // RFC 2616 (section 14.4) defines the Accept-Language header as follows:
    //   Accept-Language = "Accept-Language" ":"
    //                  1#( language-range [ ";" "q" "=" qvalue ] )
    //   language-range  = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )
    // Samples: "hu, en-us;q=0.66, en;q=0.33", "hu,en-us;q=0.5"
    $browser_langcodes = array();
    if (preg_match_all('@(?<=[, ]|^)([a-zA-Z-]+|\\*)(?:;q=([0-9.]+))?(?:$|\\s*,\\s*)@', trim($_SERVER['HTTP_ACCEPT_LANGUAGE']), $matches, PREG_SET_ORDER)) {
        foreach ($matches as $match) {
            // We can safely use strtolower() here, tags are ASCII.
            // RFC2616 mandates that the decimal part is no more than three digits,
            // so we multiply the qvalue by 1000 to avoid floating point comparisons.
            $langcode = strtolower($match[1]);
            $qvalue = isset($match[2]) ? (double) $match[2] : 1;
            $browser_langcodes[$langcode] = (int) ($qvalue * 1000);
        }
    }
    // We should take pristine values from the HTTP headers, but Internet Explorer
    // from version 7 sends only specific language tags (eg. fr-CA) without the
    // corresponding generic tag (fr) unless explicitly configured. In that case,
    // we assume that the lowest value of the specific tags is the value of the
    // generic language to be as close to the HTTP 1.1 spec as possible.
    // See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4 and
    // http://blogs.msdn.com/b/ie/archive/2006/10/17/accept-language-header-for-internet-explorer-7.aspx
    asort($browser_langcodes);
    foreach ($browser_langcodes as $langcode => $qvalue) {
        $generic_tag = strtok($langcode, '-');
        if (!isset($browser_langcodes[$generic_tag])) {
            $browser_langcodes[$generic_tag] = $qvalue;
        }
    }
    // Find the enabled language with the greatest qvalue, following the rules
    // of RFC 2616 (section 14.4). If several languages have the same qvalue,
    // prefer the one with the greatest weight.
    $best_match_langcode = FALSE;
    $max_qvalue = 0;
    foreach ($languages as $langcode => $language) {
        // Language tags are case insensitive (RFC2616, sec 3.10).
        $langcode = strtolower($langcode);
        // If nothing matches below, the default qvalue is the one of the wildcard
        // language, if set, or is 0 (which will never match).
        $qvalue = isset($browser_langcodes['*']) ? $browser_langcodes['*'] : 0;
        // Find the longest possible prefix of the browser-supplied language
        // ('the language-range') that matches this site language ('the language tag').
        $prefix = $langcode;
        do {
            if (isset($browser_langcodes[$prefix])) {
                $qvalue = $browser_langcodes[$prefix];
                break;
            }
        } while ($prefix = substr($prefix, 0, strrpos($prefix, '-')));
        // Find the best match.
        if ($qvalue > $max_qvalue) {
            $best_match_langcode = $language->language;
            $max_qvalue = $qvalue;
        }
    }
    return $best_match_langcode;
}

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