We are currently running php 4.3.10 and would like to upgrade to php 5.x.x. I have read the posts on how to run 4 and 5 side by side, but we really are not interested in doing this, we just want to use version 5. My question is how do we determine if it will break certain php scripts/apps, such as oscommerce, fantastico as well as it's applications, WHMAutopilot, and some of our clients own custom php scripts. For those of you who have already made the switch, did you encounter any problems? Did you give your users notice before making the change? If so, how long of a notice? If we upgrade to 5 and we find that it breaks too much, is it easy to move back to version 4 without any difficulties?