Get current user

http://docs.joomla.org/JFactory/getUser

$user =& JFactory::getUser();

if (!$user→guest) {
echo 'You are logged in as:<br />';
echo 'User name: ' . $user→username . '<br />';
echo 'Real name: ' . $user→name . '<br />';
echo 'User ID : ' . $user→id . '<br />';
}