Piwik\Common::extractLanguageCodeFromBrowserLanguage PHP Method

    public static function extractLanguageCodeFromBrowserLanguage($browserLanguage, $validLanguages = array())
    {
        $validLanguages = self::checkValidLanguagesIsSet($validLanguages);
        $languageRegionCode = self::extractLanguageAndRegionCodeFromBrowserLanguage($browserLanguage, $validLanguages);
        if (strlen($languageRegionCode) == 2) {
            $languageCode = $languageRegionCode;
        } else {
            $languageCode = substr($languageRegionCode, 0, 2);
        }
        if (in_array($languageCode, $validLanguages)) {
            return $languageCode;
        }
        return self::LANGUAGE_CODE_INVALID;
    }

 protected function aggregateByLanguage()
 {
     /** @var RegionDataProvider $regionDataProvider */
     $regionDataProvider = StaticContainer::get('Piwik\\Intl\\Data\\Provider\\RegionDataProvider');
     $query = $this->getLogAggregator()->queryVisitsByDimension(array("label" => self::LANGUAGE_DIMENSION));
     $countryCodes = $regionDataProvider->getCountryList($includeInternalCodes = true);
     $metricsByLanguage = new DataArray();
     while ($row = $query->fetch()) {
         $langCode = Common::extractLanguageCodeFromBrowserLanguage($row['label']);
         $countryCode = Common::extractCountryCodeFromBrowserLanguage($row['label'], $countryCodes, $enableLanguageToCountryGuess = true);
         if ($countryCode == 'xx' || $countryCode == $langCode) {
             $metricsByLanguage->sumMetricsVisits($langCode, $row);
         } else {
             $metricsByLanguage->sumMetricsVisits($langCode . '-' . $countryCode, $row);
         }
     }
     $report = $metricsByLanguage->asDataTable();
     $this->insertTable(self::LANGUAGE_RECORD_NAME, $report);
 }