New to CI, how to extend Libraries and helpers?

[eluser]CroNiX[/eluser]
To extend core files
Creating/Extending Core Classes

Extensions to core classes go in /application/core and are prefixed with "MY_"

To modify Libraries (See "Replacing Native Libraries with Your Versions"):
Creating Libraries
Extensions to libraries go where your custom libraries go, /application/libraries

You can extend helpers the same way, but they obviously go in the /application/helpers dir.