Hello John,

Hosting provider response: I can assure you that the PHP warning indicates that the call is being made to the link, and Facebook is returning a 403 error. "failed to open stream: HTTP request failed! HTTP/1.1 403 Forbidden" This is the integral piece of the PHP warning. This means that the other web-server returns the 403 status code. This is not an internal error that indicates problems with PHP itself.

When I first enabled the Facebook Share button, no errors were appearing, and I could curl the URL without error. Only after it indicated that Facebook was ratelimiting the URL did the 403 errors show up. Upon enabling the facebook share button once more, there did not appear to be any errors. This reinforces the ratelimit information. If your developer is unable to offer further information, you might try contacting Facebook support for more information about the ratelimiting and how it occurs.

While we're happy to help, we're not developers, so much of this falls outside our scope of support. We're frequently limited by what we see when reviewing the server itself.