Regarding(read-line):

You can use(php/readline) if you haveext-readline installed. I will not wrap this function in the core library because it requires a extension.

Regarding an io:

In the clojure / Java world it makes sense to wrap thejava.io library because it is well defined and used very often in a lot of code. In PHP the io utils are much simpler. I would recommend to use them directly (e.g.(php/file_get_contents "path/to/file") or(php/file_put_contents "path/to/file" "content")). However, if you have a cool idea on how to make a very good io library you can just create a library for it in an extra repository.

In general I want to keep the core library of Phel small. I would like to focus on stuff that requires as common specification (like the request and response object) or very general functions and macros. Moving libraries in extra repositories has also the benefit that new versions can be published independently from the compiler.