[eluser]jedd[/eluser]
[quote author="mradlmaier" date="1253413957"]
Maybe the native PHP function will do the job, though. Just was hoping to reuse CI system code, because that would be more elegant...
[/quote]
I don't imagine there's any CI code to reuse here, as the CI session library isn't intended as an ersatz user table. If you want to record information about your users, use a real user table.
You could, as PistolPete intimated, just run through the contents of your ci_session table and unserialize() the user_data column. Identifying that back to a given user might be challenging, as the ci_session table doesn't rely on your application's understanding of user id's. Presumably you just keep that somewhere in the user_data array - though it's getting messier, huh. Sure you want to do it this way rather than doing it properly?