How to implement code highlighting features ?

[eluser]WanWizard[/eluser]
No, geshi is just a highlighter.

You have to create the proper CSS code for geshi to work with, then use some technique ( for example a preg_match() ) to get the code blocks from the text, run the code blocks through gehsi, and reinsert them into the text. Geshi output will contains lots of span's that uses CSS to highlight.

Check the docs on the Gehsi site, they explain everything.