I'm trying to setup a Paypal Express Checkout payment in a PHP website. I've setup the payment flow as stated in Paypal documentation. Additionally, I've setup a IPN callback to catch transactions on vendor account.
Now I'm wondering how to detect when buyer has insufficient funds to complete payment. Should I check PAYMENTINFO_n_PAYMENTSTATUS for any pending reason? Is IPN callback invoked with some particular status in this case?