If you are working with the custom Magento development/Extension Development then It’s very important to know regarding the session in Magento, In this post I am trying to cover Get Session, Set Session and Unset Session In Magento.
Suppose you want to set a custom session with Variable Name ‘testing_magento’. The session value here is ‘EWA’ then the syntax will be:

Set Session In Magento:

Mage::getSingleton('core/session')->setTestingMagento('EWA');

Get session testing_magento

$test = Mage::getSingleton('core/session')->getTestingMagento();

Unset Session In Magento

Mage::getSingleton('core/session')->setTestingMagento();

(You can use customer or core session in frontend. Use adminhtml session in the backend.)

Core Session In Magento

Mage::getSingleton('core/session');

Customer Session In Magento:

Mage::getSingleton('customer/session');

Admin Session In Magento:

Mage::getSingleton('adminhtml/session');

Hope this will be helpful, Thanks and Enjoy the Magento Custom Coding