joomla外部php代码，用于登录用户数据

Question

define('_JEXEC', 1);
define('JPATH_BASE', realpath(dirname(__FILE__)));
require_once ( JPATH_BASE .'/includes/defines.php' );
require_once ( JPATH_BASE .'/includes/framework.php' );
require_once ( JPATH_BASE .'/libraries/joomla/factory.php' );
$user = JFactory::getUser();   
echo 'User name: ' . $user->username . '<br />';     
echo 'Real name: ' . $user->name . '<br />';
$specificuser = JFactory::getUser(42);
echo 'Specific User name: ' . $specificuser->username . '<br />';
echo 'Specific Real name: ' . $specificuser->name . '<br />';

I have added this code in my external php file. The $specificuser code is working; but sometimes the $user output is shown, sometimes it isn't. Any idea of the problem? output is here:

User name: 
Real name: 
Specific User name: user
Specific Real name: Super User

Answer 1

JFactory::getUser() method loads current user object:

• When you are logged in: it will return your data.
• When you are logged out: you are a guest / anonymous visitor without a name.

Second case also applies when you log in, but your session expires.

Answer 2

You don't start the Joomla! application, so session handling and other things do not work.

See my answer to a similar question for a working example on how to initialize Joomla! correctly.