Just extract the CodIgniter code into a webserver directory and create the controller code to show some output or load a view and you are done!
http://en.wikipedia.org/wiki/Transformation_of_text#Upside-d...
For a demonstration, see http://www.sevenwires.com/play/UpsideDownLetters.html
http://lab.arc90.com/experiments/readability/
(Not flames, just burning pain...)
http://twitter.com/github/status/8551643423