I'm looking to find a REPL system that can be executed on a web page and that the server can react to. Is there anything out there (I'd assume it would have to be using Javascript/AJAX)? If there's a PHP implementation, it would be even more awesome, but for now I'm just looking for some kind of an implementation.
A JavaScript REPL: http://tech.einaregilsson.com/repl.html
A PHP REPL developed at Facebook: http://www.phpsh.org/
A Python REPL: http://www.trypython.org/
A Ruby REPL: http://tryruby.org/
A Haskell REPL: http://tryhaskell.org/
An R REPL: http://rstudio.org/