Info: As KCFinder's documentation mentions, if your application (Yii in our case) session handling is using the PHP environment configuration - meaning no change in session handling at all, then no change is needed also on KCFinder side to be able to use this session and thus have this simple interface between your Yii webapp and KCFinder. If that's your case then you probably need not read the rest of this article but rather just make sure that before a user attempts to upload or browse your server a session variable is already set for him (or her) with his specific configuration already waiting for KCFinder there. What can this session interface be useful for? For example, for having per-user upload directory. You could have uploadURL variable established in the session variable to contain the user's id. When an upload or browse use case will occur, the client side will trigger the KCFinder completely decoupled from the Yii application. Yet, since you've already synced your user-specific-configuration with KCFinder via the session, KCFinder will pick it up and use it.
In many cases developers of one project use their own local environments for coding. There may be a common test platform and, of course, production. All these environments usually have different DB credentials and directory structures (first of all, path to YII framework directory). Another feature is debugging. It's convenient to turn it on for local environments, eventually - on the test server and never (generally speaking) - on the production.