How can I diferentiate between guests and members?

Question

How can I execute a different code in my plugin depending on if the user is logged in or not in Joomla? Basically I want to do this:

<?php
if (loggedin) {
   // Do something 
}
else {
   // Do something else 
}
?>

Answer 1

I usually do something like this:

<?php
$user = JFactory::getUser();
if ($user->guest) {
    // User is not logged in
        } else {      
    //User is logged in
        }
?>

Take a look at the Joomla Documentation.

Answer 2

You can either use this:

$user = JFactory::getUser();
if($user->id != 0)
{
    // you are a member
}
else 
{
    // you are a guest
}

or this:

$user = JFactory::getUser();
if($user->guest)
{
    // you are a guest
}
else 
{
    // you are a member
}

Bother are the same with most likely nano seconds in performance, in regards to speed.

Answer 3

Besides the direct programmatic method to conditionally show different contents (JFactory::getUser()->guest), there's an alternative to create a Guest group to identify this specific set of users; in this way, the content can be managed either at the CMS level with the regular administrative tools or in a plugin with Access Control List controls:

How do you hide something from logged in users? http://docs.joomla.org/How_do_you_hide_something_from_logged_in_users%3F

Associated routine to check if the user belongs to the Guest group:

$user = JFactory::getUser();
$groups = JAccess::getGroupsByUser(user->id, false);
if (in_array(MY_GUEST_GROUP, $groups))
{
   echo 'Only visible for guests';
}