I recently installed the popular forum software, phpBB3(RC7), on my server. I knew that I wouldn't get a ton of traffic at first, so that's why I decided on the release candidate version (RC7) vs. the stable phpBB2. After a week or two, the stable version 3 (Olympus) was released and I was very interested in upgrading. At this point, I had made a ton of modifications to the many files contained in the phpBB3 directories. I was worried that if I upgraded, my files would all be replaced with the new ones from the stable version. My solution was to set up a "non-production" server to test out the upgrade.
I downloaded the upgrade package from phpBB's (3.0.0) download page. After uploading the /install directory and it's contents to the server, I pointed my web browser to http://myserver/phpBB3/install/ to begin the process. The current version of phpBB is checked and then the database is updated. This portion of the upgrade took only a few seconds.
The next step is what I was waiting for:
The upgrade scripts check for file differences.
After the differences are collected, the option to merge, existing and new files, is given.
It gives you the option to:
Merge, Use The New File, or Keep The Old
Merge is selected by default.
The script can use the File Transfer Protocol to upgrade/merge your files. This was very easy. Just enter your username, password and path.
All of my files were successfully merged, which preserved ALL of my previous modifications. I am now fully upgraded to phpBB version 3.0.0/Olympus.