This will allow for ultimate customization and compatibility with other cookie encoding functions.

It could be added as an extension to Cookies.withConverter() to allow specifying an encoding function too.

For example, the incompatibility with PHP cannot be resolved because this JS library will always store "+" signs in plain text, while PHP will always convert them to spaces when read.

In PHP, both $_COOKIE and filter_input(INPUT_COOKIE) will return already decoded value, where all "+" signs will be converted to spaces. There is a setrawcookie, but no getrawcookie function, so no way around it in PHP (without having to manually double encode and decode in both languages).