In ecommerce, when checkout product click button "Place order and make payment" is error :

Notice: Undefined index: action_ChangeCountry in D:\xampp\htdocs\silverstripe\ecommerce\code\OrderForm.php on line 272

Notice: Undefined index: action_ChangeCountry2 in D:\xampp\htdocs\silverstripe\ecommerce\code\OrderForm.php on line 272

Notice: Undefined index: Password in D:\xampp\htdocs\silverstripe\ecommerce\code\OrderForm.php on line 193

Notice: Undefined index: ConfirmPassword in D:\xampp\htdocs\silverstripe\ecommerce\code\OrderForm.php on line 193

FATAL ERROR: session_regenerate_id() [function.session-regenerate-id]: Cannot regenerate session id - headers already sent
At line 226 in D:\xampp\htdocs\silverstripe\sapphire\security\Member.php

session_regenerate_id()
line 226 of Member.php

Member::session_regenerate_id()
line 244 of Member.php

Member->logIn()
line 206 of OrderForm.php

OrderForm->processOrder(Array,OrderForm)
line 197 of Controller.php

Controller->run(Array)
line 15 of ModelAsController.php

ModelAsController->run(Array)
line 76 of Director.php

Director::direct(/checkout/)
line 104 of main.php

Context

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Debug (Debug::showError() in line 149 of Debug.php)

Pls, who can fix error, thanks.