Logger

config/packages/logger.php wires the Monolog logger and binds it to LoggerInterface.

What it does

• Creates a StreamHandler writing to logger.path.
• Wraps the stream handler in a FingersCrossedHandler that buffers log records and only flushes them when a record at or above the configured level is emitted.
• Derives the minimum log Level from app.debug: Level::Debug in debug mode, Level::Warning in production.
• Creates a Logger named after app.name and binds it to LoggerInterface.

Configuration parameters

Key	Default	Description
logger.path	php://stderr (from services.php)	Log output destination. Accepts any PHP stream wrapper or a file path.
logger.handlers	[FingersCrossedHandler] (from services.php)	Monolog handlers attached to the logger. Other packages or services.php can append additional handlers via add([...]).

Log levels by environment

app.debug	Minimum level
true (dev)	Debug — all messages are written.
false (prod)	Warning — only warnings and above trigger a flush.

Writing logs to a file

// services.php
'logger.path' => string('{app.project_root}/var/log/app.log'),

Adding a handler

// services.php
use Monolog\Handler\SlackWebhookHandler;
use function DI\add;
use function DI\create;

'logger.handlers' => add([
    create(SlackWebhookHandler::class)->constructor('https://hooks.slack.com/...'),
]),

Dependencies

Package	Description
monolog/monolog	The logging library.