If the wrong session is used, it is because the session_name is wrong. The session name is set in Mage_Core_Model_Session_Abstract_Varien::setSessionName().
But after a look on the Stacktrace, I have no idea, why overwriting _construct or even __construct should be a problem here:
#0 Mage_Core_Model_Session_Abstract_Varien->setSessionName(frontend) called at [app/code/core/Mage/Core/Model/Session/Abstract/Varien.php:111]
#1 Mage_Core_Model_Session_Abstract_Varien->start(frontend) called at [app/code/core/Mage/Core/Model/Session/Abstract/Varien.php:166]
#2 Mage_Core_Model_Session_Abstract_Varien->init(core, frontend) called at [app/code/core/Mage/Core/Model/Session/Abstract.php:84]
#3 Mage_Core_Model_Session_Abstract->init(core, frontend) called at [app/code/core/Mage/Core/Model/Session.php:42]
#4 Mage_Core_Model_Session->__construct(Array ([name] => frontend)) called at [app/code/core/Mage/Core/Model/Config.php:1348]
#5 Mage_Core_Model_Config->getModelInstance(core/session, Array ([name] => frontend)) called at [app/Mage.php:462]
#6 Mage::getModel(core/session, Array ([name] => frontend)) called at [app/Mage.php:476]
#7 Mage::getSingleton(core/session, Array ([name] => frontend)) called at [app/code/core/Mage/Core/Controller/Varien/Action.php:494]
#8 Mage_Core_Controller_Varien_Action->preDispatch() called at [app/code/core/Mage/Core/Controller/Front/Action.php:64]
#9 Mage_Core_Controller_Front_Action->preDispatch() called at [app/code/core/Mage/Core/Controller/Varien/Action.php:408]
#10 Mage_Core_Controller_Varien_Action->dispatch(view) called at [app/code/core/Mage/Core/Controller/Varien/Router/Standard.php:250]
#11 Mage_Core_Controller_Varien_Router_Standard->match(Mage_Core_Controller_Request_Http Object ([] => /test.html,[] => ,[] => /test.html,[] => ,[] => ,[] => Array (),[] => catalog,[] => ,[] => Mage_Catalog,[] => ,[] => Array (),[] => Array ([0] => _GET,[1] => _POST),[] => /catalog/product/view/id/21,[] => ,[] => ,[] => catalog/product/view/id/21,[] => Array ([id] => 21),[] => ,[] => Array ([rewrite_request_path] => test.html),[] => 1,[] => catalog,[] => module,[] => product,[] => controller,[] => view,[] => action)) called at [app/code/core/Mage/Core/Controller/Varien/Front.php:176]
#12 Mage_Core_Controller_Varien_Front->dispatch() called at [app/code/core/Mage/Core/Model/App.php:354]
#13 Mage_Core_Model_App->run(Array ([scope_code] => ,[scope_type] => store,[options] => Array ())) called at [app/Mage.php:683]
#14 Mage::run(, store) called at [index.php:87]
So I found out the problem with the customer session was that I was instantiating my own custom session way to early. As I learned from this article by Alan Storm, instantiating sessions too early can break session storage, so different pages where accessing different sessions. That's why sometimes I didn't get the correct customer session data.
I was trying to use a session object in a custom router and found it's a big NO. I changed my router code to instead set a POST param to pass on my value and then store it to the session later on in the process.
P.S. My custom session is still buggy, since it appears its data is only accessible in the page request that set it and not any other subsequent requests, but the customer session is okay now so that's half the problem gone.
Best Answer
Sounds like the cookie containing the session named
frontendis not available on yourabc.phpscript.Make sure the cookie path in your Magento installation is set to
/underSystem > Configuration > Web > Session Cookie Management > Cookie Pathand install an extension in your browser that can easily display cookies. In chrome I use edit this cookie.