Per PHP's Throwable RFC, a change has been made in PHP 7's error handling. Long and short, the BaseException class is gone and the two error branches (Exception and Error (previously EngineException)) now implement the Throwable interface. This PR updates our adoption of the previous exception objects to follow the newly implemented interfaces.
Note that this change is now implemented in the PHP 7 branch. Travis-CI (as of the time this was opened) may not yet be updated with this change.
Merged on review.