This is just a heads up for anyone who was having a problem with integration since the 1.2.7 upgrade of Zen Cart, like I was. Nothing I did solved the issue. I tried all of the suggestions, including having both Zen Cart and PHPBB in the same database. None of it worked.

Here is what worked.

1. I installed a fresh, unedited copy of BOTH Zen Cart and PHPBB (I've tried this now both ways, using separate databases and just separate table prefixes in the same database, it works in both cases), making sure I had the latest version of both before proceeding any further. I was up to date, so....

2. I tested the integration by entering several new members to the cart. They all showed up as new forum members. So far, so good.

3. I copied ALL of the database information from the already existing databases for both into the new database(s), but I only imported the data, not the structure (this was the problem, something in the structure of one of these pieces of software was conflicting with the other. I have no idea what it was.) After getting past the "Duplicate entry" issue because I was copying myself as admin over the existing admin, also myself, (as Homer would say, "DOH!"), I managed to swap over all of the data from the cart and the forum into the new database. This resolved all of my previous issues with integration and it has been working fine for a few weeks now.

I also noticed a possible reason for my initial problem. When I went back to playing with the old cart and forum, which were still both installed and working (except for the integration issue) on the website where this problem was detected originally, I noticed that if I rolled back the versions of Zen Cart and tried upgrading again, I got several SQL error messages during the upgrades. If I went into the database and checked, the updates I could look at were successful, yet the page kept tossing errors. I checked the SQL before and after the upgrades (I had several copies of the database in various stages of upgrading, so I could see side-by-side what was going on) and the chenges were definitely being made... The only problem was, for some reason, one of the upgrades neglected to add one new table, so each time I ran an upgrade, it tried to write into that table, which didn't exist. Going directly into the database gave me the chance to spot the missing table and also allowed me to create it since the upgrade wasn't doing it... For some reason, the error messages were not giving me that clue. They usually do that.

I went way back to 1.2.6 (or older, I forget now) and started over. I must have missed an upgrade along the way the first time, because now both the old and the new system are working fine. Maybe in the future, you can add levels to the upgrade scripts like PHPBB does so those of us that miss an upgrade or three can jump to the current level instead of having to install each upgrade until we reach the latest version? I won't let it happen again, but I'm not the only one who missed an upgrade, I'm sure.

One other thing I noticed. If I run the SQL patches from the admin panel, the system adds a second zen_ prefix to the new tables it creates. For example, the SQL error table zen_upgrade_exceptions becomes zen_zen_upgrade_exceptions. I have to go into the database and remove the extra zen_ prefix from any new table or the cart does not get upgraded. If I run the SQL script through phpMyAdmin, it does not add the extra zen_ prefix. The admin panel SQL upgrade does not change any of the existing tables, only tables that are created during the upgrade. It's not a problem for me since I know how to get around it now, but it was a bit confusing at first. I just run all upgrade scripts through phpMyAdmin now. Problem solved.

I hope some of this helps someone who may be arm-wrestling with integration like I was.