Is there a library that ....

[eluser]pickupman[/eluser]
With my library, you don't need to edit any other files or add the autoload function in config.php. Just unzip the library into your folder, and use as shown. I've tried it and have it outputting the code how I expected. Did you have any errors with my download/example?

Check your camel case on how your are spelling geshi. If you are going cahvas method, you will need to reference GeSHi with the proper case as declared by the class name, not by the filename.

With my library, it would use all lower case references, and used just like all other libraries in CI.

Also, you may want to try htmlentities($code).