openssl and self signed ssl certs

I am using a php oauth library which is trying to make secure 
connections to the oauth server and failing I think because the 
oauth server uses a self signed cert. How do get php/openssl to 
trust the cert... where do I import the cert. The cert store is 
obvious in the openssl implementation I compiled php to use, but 
where is the cert store when using php/openssl?

Any help appreciated please.