If you’re working in the web development sector, chances are that you will need to display code snippets on your WordPress website from time to time.

Don't try do it yourself use this plugin:

Enlighter is a free, easy-to-use, WordPress plugin which provides syntax highlighting. Highlighting is powered by the EnlighterJS javascript library to provide a beautiful code appearance.

WHY?

Its free! works well and you have more important things to be doing!