message-structure.md

Log message structure

Within monolog log messages are passed around as Monolog\LogRecord objects, for example to processors or handlers.

The table below describes the properties available.

property	type	description
message	string	The log message. When the PsrLogMessageProcessor is used this string may contain placeholders that will be replaced by variables from the context, e.g., "User {username} logged in" with ['username' => 'John'] as context will be written as "User John logged in".
level	Monolog\Level case	Severity of the log message. See log levels described in 01-usage.md.
context	array	Arbitrary data passed with the construction of the message. For example the username of the current user or their IP address.
channel	string	The channel this message was logged to. This is the name that was passed when the logger was created with new Logger('channel').
datetime	Monolog\DateTimeImmutable	Date and time when the message was logged. Class extends \DateTimeImmutable.
extra	array	A placeholder array where processors can put additional data. Always available, but empty if there are no processors registered.

At first glance context and extra look very similar, and they are in the sense that they both carry arbitrary data that is related to the log message somehow. The main difference is that context can be supplied in user land (it is the 3rd parameter to Psr\Log\LoggerInterface methods) whereas extra is internal only and can be filled by processors. The reason processors write to extra and not to context is to prevent overriding any user-provided data in context.

All properties except extra are read-only.

Note: For BC reasons with Monolog 1 and 2 which used arrays, LogRecord implements ArrayAccess so you can access the above properties using $record['message'] for example, with the notable exception of level->getName() which must be referred to as level_name for BC.