I am experimenting with Pat_Patterson's "Interact with the Force.com REST API from PHP". I am using PHP Version 5.6.3 , and I already registered my app via Setup->Create->Apps->Connected Apps. I setup the Redirect URL, Customer Secrets and Consumer Keys in the Config.php file but when I run the code it gives me an error:
Error: call to token URL https://login.salesforce.com/services/oauth2/token failed with status 0, response , curl_error SSL certificate problem: unable to get local issuer certificate, curl_errno 60
Can someone explain what this error means and what steps are necessary to address it?