Checking if a user is logged in to a different CodeIgniter app

[arashsaffari]

I have the following question: I have two CodeIgniter applications. The first application (App1) is accessible at www.mydomain.com and has access to the db1 database. The second application (App2) is located at www.mydomain.com/otherapp (on the same domain as App1, but in a different path) and has access to the db2 database. Users can log in to App1 using CI Shield. Now, I want to determine the best way to check in App2 whether a user is logged in to App1. What would be the best way to accomplish this?