"Python has one. Ruby has one. Clojure has one. Now PHP has one, too. Boris is PHP's missing REPL (read-eval-print loop), allowing developers to experiment with PHP code in the terminal in an interactive manner. If you make a mistake, it doesn't matter, Boris will report the error and stand to attention for further input.

Everything you enter into Boris is evaluated and the result inspected so you can understand what is happening. State is maintained between inputs, allowing you to gradually build up a solution to a problem."