"PHP has been in great need of a decent shell environment for some time now", Demian Turner writes. Jan Kneschke has come to the rescue and implemented PHP Shell in userland PHP, which provides many of the features that come by default in the interactive shells of languages like Python and Ruby.

Demian mentions that PHP Shell is made available as a PEAR library, so it's just a matter of executing the php-shell.sh script, which is discoverable in your PATH if you're using Linux (or there is a cmd equivalent for Windows users).