If anExceptionobject is passed in the context data, it MUST be in the'exception'key. Logging exceptions is a common pattern and this allows implementors to extract a stack trace from the exception when the log backend supports it. Implementors MUST still verify that the'exception'key is actually anExceptionbefore using it as such, as it MAY contain anything. (https://www.php-fig.org/psr/psr-3/#13-context)