Develope a Favorite Friends Feature

I currently have a website called Skill Land ([login to view URL]) and I would like to have a "friend" feature added to the site. This "friends" feature is similar to the Youtube "friednds" feature with the following requirement: The php script I am using is called phpmydirectory which is located at [login to view URL] 1. A registered user can add other registered users to their "friends" folder 2. A registered user can invite NON-registered users to signup, and be added to the "friends" folder 3. Once added to the "friends", the foder owner can private message the users that are on the folder and vise versa. 4. The users that are on the "friends" folder are listed first with the logo (picture that they use) next to the name. 5. The "friends" folder can be organized by different categories. If you want to see I am want, visit youtube and see their friends feature. The only thing different is I want the folder owners to have the ability to sort the users in the folder by various cateogries similar to how we sort emails.