public static function extractPluralsForms($header)
    {
        $headers = explode("\n", $header);
        $expr = 'nplurals=2; plural=n == 1 ? 0 : 1;';
        foreach ($headers as $header) {
            if (stripos($header, 'Plural-Forms:') === 0) {
                $expr = substr($header, 13);
            }
        }

        return $expr;
    }