Jetpack::guess_locale_from_lang PHP Method

    function guess_locale_from_lang($lang)
    {
        if ('en' === $lang || 'en_US' === $lang || !$lang) {
            return 'en_US';
        }
        if (!class_exists('GP_Locales')) {
            if (!defined('JETPACK__GLOTPRESS_LOCALES_PATH') || !file_exists(JETPACK__GLOTPRESS_LOCALES_PATH)) {
                return false;
            }
            require JETPACK__GLOTPRESS_LOCALES_PATH;
        }
        if (defined('IS_WPCOM') && IS_WPCOM) {
            // WP.com: get_locale() returns 'it'
            $locale = GP_Locales::by_slug($lang);
        } else {
            // Jetpack: get_locale() returns 'it_IT';
            $locale = GP_Locales::by_field('facebook_locale', $lang);
        }
        if (!$locale) {
            return false;
        }
        if (empty($locale->facebook_locale)) {
            if (empty($locale->wp_locale)) {
                return false;
            } else {
                // Facebook SDK is smart enough to fall back to en_US if a
                // locale isn't supported. Since supported Facebook locales
                // can fall out of sync, we'll attempt to use the known
                // wp_locale value and rely on said fallback.
                return $locale->wp_locale;
            }
        }
        return $locale->facebook_locale;
    }