Isn't returning boolean false or null (void) but never boolean true an inconsistent return behaviour? I would expect a method that indicates to return a boolean value to return both states. But I agree that `\Doctrine\DBAL\Connection` should not return any value as this is not necessary as you mentioned.
I think that the `PingableConnection::ping()` method should have a more descriptive DocBlock to make clear what to return in which case.