Whilst working on a project recently I hit upon a PHP error that I've never seen before. During a process where a soap service was calling an API the connection would fail and the program would fatal error and stop.
I had protection mechanisms in place to catch this kind of connection error, but the fatal error was caused when the program tried to throw the exception I had put in place to indicate a failed connection.
Here is the error message (with some of the detail removed). This is a Drupal site but that detail is irrelevant to the problem.