I tried to use the package paypal/rest-api-sample-app-php to make sure if the problem is in my code. apparently it's not.. so I tried to:
curl -v https://api.sandbox.paypal.com/v1/oauth2/token
and I received an error. this is what I runned on my cmd:
C:\Users\Eliya Cohen>curl -v https://api.sandbox.paypal.com/v1/oauth2/token
* Trying 173.0.82.78...
* Connected to api.sandbox.paypal.com (173.0.82.78) port 443 (#0)
* ALPN, offering http/1.1
* Cipher selection: ALL:!EXPORT:!EXPORT40:!EXPORT56:!aNULL:!LOW:!RC4:@STRENGTH
* successfully set certificate verify locations:
* CAfile: C:\Program Files\cURL\bin\curl-ca-bundle.crt
CApath: none
* TLSv1.2 (OUT), TLS header, Certificate Status (22):
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (OUT), TLS alert, Server hello (2):
* SSL certificate problem: unable to get local issuer certificate
* Closing connection 0
* TLSv1.2 (OUT), TLS alert, Client hello (1):
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: http://curl.haxx.se/docs/sslcerts.html
curl performs SSL certificate verification by default, using a "bundle"
of Certificate Authority (CA) public keys (CA certs). If the default
bundle file isn't adequate, you can specify an alternate file
using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
the bundle, the certificate verification probably failed due to a
problem with the certificate (it might be expired, or the name might
not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
the -k (or --insecure) option.
this is my curl-ca-bundle.crt file: http://pastebin.com/RZ6EaxTF
The cert file you give in your pastebin contains the necessary root certificate. Which means that you either don't use the CA file given in the pastebin or that there is some middlebox in your connection to paypal which does SSL interception. This could be a man in the middle attack but more common is SSL interception inside companies, so that the company can analyse encrypted traffic for malware. If your are inside a company please check with your network administrators.
I was getting the same error, But after enabling the ssl in the tomcat server, it is gone. return url you are supposed to use