The following is a tutorial on how to set cookies when installing Photopost with an external forum so that cookies can be read over all subdomains.
Number one mistake made is people have their forums or galleries installed on subdomains etc and the cookie login will be dropped when going back and forth.
To ensure cookies are set the same in both Photopost and your forum you can do this before installing Photopost.
Go to your forum admin and set your cookies like so.
cookie path = /
This ensures the cookie is read across the whole domain.
cookie prefix = ??
This is only needed if your forum has a cookie prefix like in invisionboard vbulletin etc. Example in vbulletin this is found in your vbulletin config.php file in the includes subdirectory of your vb install. Usually it is bb.
cookie domain = .yoursite.com
This will ensure that the cookie is read over any subdomain on the master domain yourdomain.com
Now that is it on forum cookie settings. There is one additional note though. In phpbb3, wowBB and SMF they use a cookie name which is an additional setting. They do not have a cookie prefix. You will want to write down the cookie name before installing Photopost Products.
Next after you have set your forum cookies correct you can logout and login again to generate the proper new cookies.
You would then go about installing Photopost Products per our installation instructions here.
PhotoPost PHP Photo Sharing Photo Gallery Installation Guide
Now on install at step 4 you can make sure to either enter the correct cookie prefix or cookie name depending on the forum installation and once you run through install you should be cookied in and set the Photopost cookie domain as noted to .yoursite.com in Admin => Cookie Settings.
Once you do this you should have no issues with cookies or dropped logins.