How do I save value in my own session variable in Magento?

I am using Magento and trying to save a value in the session as follows in its index.php file, but the value is not being retained.

$_SESSION['myvar'] = '1';

How do I do it?

Thanks

Solution 1:

Let's say you want to save the value "Hello world" to the "welcome message" variable in the session. The code would be :

$inputMessage = 'Hello World';
Mage::getSingleton('core/session')->setWelcomeMessage($inputMessage);

Now you want to echo the "welcome message" somewhere else in your code/site.

$outputMessage = Mage::getSingleton('core/session')->getWelcomeMessage();
echo $this->__($outputMessage);

Solution 2:

Following the example given by Ali Nasrullah, I would do:

$session = Mage::getSingleton("core/session",  array("name"=>"frontend"));
// set data
$session->setData("device_id", 4);
// get data
$myDeviceId = $session->getData("device_id");

Make sure you include [Mage-root]/app/Mage.php befor calling the code above!

@Ali Nasrullah: Pass the value of device:id as second parameter of the setData function.