Using this code (pasted from this tutorial), I get a successful PayPal DoDirectPayment method execution. Note that CURLOPT_SSL_VERIFYPEER is set to FALSE.
However when I set the normal value (CURLOPT_SSL_VERIFYPEER = TRUE) I get no response from PayPal, not even a failure response, despite the fact that my code operates on a server with a working SSL certificate (all pages work with HTTPS URLs).
Anybody knows what could cause this problem ?