问题
while checking the paypal ipn history some of the transaction were disabled i resend them but now the http response code is empty for those transactions it should be 200. Searched through paypal documentation but didnt find anything about empty http response code.
i am using a wordpress plugin integrated with paypal api (using adaptive preapproval payment feature)
来源：https://stackoverflow.com/questions/30381242/paypal-payment-ipn-http-response-code-is-empty