Extract specific data from multidimensional array

I have a small problem. I'm trying to extract data from [user] but I can seem to get it right. Can someone please give me one example of how to extract for example the users id and from there I'm golden. This is the $_SESSION array (what the session contains), if that's any help.

 Array ( [__default] => Array ( 
                          开发者_如何转开发  [session.counter] => 3
                            [session.timer.start] => 1307209662 
                            [session.timer.last] => 1307209693 
                            [session.timer.now] => 1307209701 
                            [session.client.browser] => Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0.1) Gecko/20100101 Firefox/4.0.1 
                            [registry] => JRegistry Object ( 
                                                            [_defaultNameSpace] => session
                                                            [_registry] => Array ( 
                                                                                    [session] => Array ( 
                                                                                                        [data] => stdClass Object ( ) 
                                                                                                        ) 
                                                                                ) 
                                                            [_errors] => Array ( ) 
                                                            ) 
                            [user] => JUser Object ( 
                                                    [id] => 0 
                                                    [name] => 
                                                    [username] => 
                                                    [email] => 
                                                    [password] => 
                                                    [password_clear] => 
                                                    [usertype] => 
                                                    [block] => 
                                                    [sendEmail] => 0 
                                                    [gid] => 0 
                                                    [registerDate] => 
                                                    [lastvisitDate] => 
                                                    [activation] => 
                                                    [params] => 
                                                    [aid] => 0 
                                                    [guest] => 1 
                                                    [_params] => JParameter Object ( [_raw] => 
                                                                                    [_xml] => 
                                                                                    [_elements] => Array ( ) [_elementPath] => Array (                                                                                                                                                              [0] => C:\xampp\htdocs\libraries\joomla\html\parameter\element )
                                                                                                                                                            [_defaultNameSpace] => _default 
                                                                                                                                                            [_registry] => Array ( 
                                                                                                                                                                                    [_default] => Array ( 
                                                                                                                                                                                                        [data] => stdClass Object ( ) 
                                                                                                                                                                                                        ) 
                                                                                                                                                                                ) 
                                                                                                                                                            [_errors] => Array ( ) 
                                                                                    ) 
                                                    [_errorMsg] => [_errors] => Array ( ) 
                                                    ) 
                            [session.token] => 971893bd69fff85ea2a006788a28b15d 
                        ) 
    [referrerid] => AUPRS-JOHNDOE
    )

$user = $_SESSION['user'];
echo $user->id;

This seems to be what you need.

This would output the user name: (if there was any)

 print $_SESSION["__default"]["user"]->name;

You first need to overcome the __default key index within the $_SESSION array. Likewise is user an array key. But what the user entry contains is an object, so you need the -> object arrow thingy to finally access the name.

Also I would not rely on __default being a given. Don't know anything about Joomla, but the $_SESSION array structure might be more flexible. Hencewhy it's advisable to find a function which instead fetches the user object for you.