I am working on a project that is about 4 years old and has been written in PHP 5.2 (php was updated along the way) and MySQL 4. There is currently a test server and production server that all need to be updated to the latest stable version of PHP and MySQL5.
I have a few concerns about this update and limited experience in managing servers.
I am worried that simply upgrading MySQL and PHP on the actual servers will somehow break the company vital applications. I was wondering if this concern is a valid one and what measures I can take to quickly revert back to the older version if I have to? Also, what is the quickest way to safely complete this update?
I appreciate any suggestions.
Thanks in advance!