protected function checkLocale($locale)
    {
        $languageFound = null;
        $language = strstr($locale, '_', true);

        foreach ($this->configuration['locales'] as $availableLocale) {
            // If locale matches, the exact matching was found.
            if ($availableLocale === $locale) {
                return $availableLocale;
            }

            // Check if language (without locale) matches.
            if ($language == $availableLocale) {
                $languageFound = $availableLocale;
            }
        }

        if ($languageFound) {
            return $languageFound;
        }

        return null;
    }