Unable to load requested class: paypal_lib

[eluser]divayank[/eluser]
I am using the same library and paste all the files as described.
In sandbox mode after making successful payment from paypal when I return back to my website
this function

Code:

paypal_success()

call but it return blank POST variable.

Code:

$this->paypal_lib->add_field('return', site_url('billinginfo/paypal_success'));
$this->paypal_lib->add_field('cancel_return', site_url( 'billinginfo/paypal_cancel') );
$this->paypal_lib->add_field('notify_url', site_url('billinginfo/ipn'));

ipn is also not working. When we press "pay now" button at paypal I should get an email but I didn't get any email.