I know this is an old thread, but I just recently ran into this same problem and thought I'd post the fix since there was none here.
Here's an explanation for it.
Some (IIS) non-standard compliant servers send data in a way that causes PHP to raise "warnings". When working with apache servers communicating with IIS servers using SSL, you should lower your error_reporting level in php.ini not to include warnings.
By editing my php.ini on the error_reporting line, the error has gone away.