PHP DAO Letting users befriend eachother (technically)

Question

Let's say I have users who can befriend eachother, technically, how do I solve this using DAO in PHP?

Database:

users       |  user_friends
- userid    |  - userid_user1
- username  |  - userid_user2

PHP User object:

class User
{
  private $userid;
  private $username;

  // getters and setters
}

Should I use this method to befriend users:

$u1 = UserDAO::getInstance()->findUserById(1);
$u2 = UserDAO::getInstance()->findUserById(2);

UserDAO::getInstance()->befriendUsers($u1, $u2);

OR should I use this method:

$u1 = UserDAO::getInstance()->findUserById(1);
$u2 = UserDAO::getInstance()->findUserById(2);
$u1->befriend($u2);

// befriend method would look like this in the User object
public function befriend(User $u)
{
  UserDAO::getInstance()->befriend($this, $u);
}

Or maybe another way?

Answer 1

Actually, none. UserDAO deals with User but not with user relationships, which is a different concern.

To keep it simple, you should have another FriendsDao which will care about the friendships. Of course, you need to update the friendships when an user is deleted.