Store user state variables in Joomla 2.5/3.0

We can use JApplication class’s setUserState method or JSession class’s Registry property to store user state variables and retrieve these variables later for further processing.

Example:

$app = JFactory::getApplication();
$app->setUserState( 'myvar', $myvarvalue );
$app->setUserState( 'com_yourcomponent.data', $yourvalue ); 

To retrieve this value, use the following code:

$app = JFactory::getApplication();
$variable = $app->getUserStateFromRequest( "com_yourcomponent.data" );

We can also store and retrieve variables in session using JFactory/getSession.

Example:

$session = JFactory::getSession();
$session->set('myvar', $myvarvalue);

It’s not a big difference and you can use whatever feels right in our context. Both methods will store the specified state in the session. The JApplication/setUserState will in fact internally use JSession/set to store the state. What JApplication/setUserState does differently is that it will store every key-value pair in a JRegistry. So it is equal to:

$session = JFactory::getSession();
$registry = $session->get('registry');
$registry->set('myvar', $myvarvalue);

So, what’s the point of using a JRegistry? It’s pretty much the functionally provided JRegistryFormat. You can use it to both parse and format the state:

$session = JFactory::getSession();
$registry = $session->get('registry');
$json = $registry->toString('JSON');
$xml = $registry->toString('XML');

It’s also worth pointing out that using JApplication/setUserState your state will end up in the “default” namespace:

$app = JFactory::getApplication();
$app->setUserState( 'myvar', $myvarvalue );
// $_SESSION['default']['registry']->set('myvar', $myvarvalue)

Source: stackoverflow.com

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