Sometimes while working with the facebook php sdk, especially when making API calls using the SDK you may come across the following error:
SSL certificate problem, verify that the CA cert is OK…… SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
Generally this happens if the bundled certificate file you are using that came with the PHP SDK download is somehow out dated or no more valid.
So the quick solution is to download the latest PHP SDK and replace your existing “fb_ca_chain_bundle.crt” file present in the src folder of the PHP SDK with the latest one. You can get the latest SDK from their github repository at https://github.com/facebook/facebook-php-sdk
Just by updating this file, the error will be resolved.