title: Isolating user uploaded contents from other users with Yii
body: <p>In my app many users, and they can add articles, articles can contain images, and all images stored in uploads folder, and by default any user can delete any image in folder, certanly its not good, whats is the best way to fix that 
  (For example store images in uploads//) or something like that?</p>
  
  <p>Problem is - how i can separate user uploads? </p>