Getting error in Curl - Peer certificate cannot be authenticated with known CA certificates
By default CURL will generally verify the SSL certificate to see if its valid and issued by an accepted CA. To do this, curl uses a bundled set of CA certificates.
If you'd like to turn off curl's verification of the certificate, use the -k (or --insecure) option. Here's an example:
curl --noproxy -k \* -D - https://127.0.0.1:443/some-secure-endpoint
For php it is possible to switch off curl's verification of the certificate (see warning below) e.g. for curl_exec
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
http://php.net/manual/en/function.curl-setopt.php
(evaluate the security risk yourself, in my case it was on a partner company's server and the file required contained no secure information - just happened to be on a secure server)