private static function capitalize($string)
    {
        $string = mb_strtolower($string);

        $string = mb_ereg_replace_callback('\b\w', function ($matches) {
            return mb_strtoupper($matches[0]);
        }, $string);

        // Lowercase 's
        $string = mb_ereg_replace_callback('\'\w\b', function ($matches) {
            return mb_strtolower($matches[0]);
        }, $string);

        return $string;
    }