I have a session class that basicly just sets and retrieves session variables, the reason I made it was so I could easily change it to use sessions or something like memcache to set the items and have them accessible on multiple pages without hitting the database

I then have this user class which uses the session object to get session variables in it.
I am wanting to add to this user class though, to make it more encapsulated I would like to be able to set the variables that I am retrieving in this class so right now I can display the userid with $user->userid; I would like to first have a method or something that sets its value from the session object I guess Does this sound lke a good idea or possibly a lot of overhead?

And if what I am trying to do is a good idea maybe you could suggest/show example of how I should do it? I am thinking that if I add that method in that possibly I should move the code in the __construct method into it's own method

Basicly, I have the variables listed in the top part of the class that are used in the construct method, if I have multiple methods in the class though would I need to set them all at the top like that?

<?PHP
//user.class.php file
class User
{
    public $userid;
    public $name;
    public $pic_url;
    public $gender;
    public $user_role;
    public $location_lat;
    public $location_long;
    public $newuser;

    function __construct()
    {
        global $session;
        if($session->get('auto_id') != ''){
            //set user vars on every page load
            $this->userid = $session->get('auto_id'); //user id number
            $this->name = $session->get('disp_name');
            $this->pic_url = $session->get('pic_url');
            $this->gender = $session->get('gender');
            $this->user_role = $session->get('user_role');
            $this->location_lat = $session->get('lat');
            $this->location_long = $session->get('long');
            $this->newuser = $session->get('newregister');
        }else{
            return false;
        }
    }
}

//with the class above I can easily show some user variables I have saved into a session like this below
$user = new user();
$user->userid;

?>

In general your idea is a good one 3 things I would do differently:

1) In your implementation doesn't seem to consider having several users. ie Several instances of the same class.

2) I would use factories instead of using IF in the constructor. So for a user you have saved in the session you would call:

 $savedUser = User::fromSession($userId);

for a new user

  $user = new User()

3) Use the serialize and unserialze functions to save that data to the session

Then your class could could be implemented as

public static function fromSession($userId) {
   return unserialize($session->get('users_'.$userId));
}

public function save() {
   return $session->set('users_'.$this->id , serialize($this));
}