meritum/logger#

meritum/logger is a minimal PSR-3 logger that writes newline-delimited JSON to stdout. It is designed for containerised environments where log aggregation is handled externally.

composer require meritum/logger

Module Registration#

Add LoggerModule to your module repository:

use Meritum\Logger\LoggerModule;

final class ModuleRepository implements ModuleRepositoryInterface
{
    public function modules(Environment $env): array
    {
        return [
            new LoggerModule(),
            // ...
        ];
    }
}

The module registers a shared Psr\Log\LoggerInterface in the container. Inject it wherever logging is needed:

use Psr\Log\LoggerInterface;

final class CreateUserHandler implements RequestHandlerInterface
{
    public function __construct(private readonly LoggerInterface $logger) {}

    public function handle(ServerRequestInterface $request): ResponseInterface
    {
        $this->logger->info('User created', ['user_id' => $user->id]);

        // ...
    }
}

Configuration#

The minimum log level is controlled by the LOG_LEVEL environment variable. If not set, it defaults to debug in Environment::Development and info in all other environments.

LOG_LEVEL=warning

Valid values (case-insensitive): debug, info, notice, warning, error, critical, alert, emergency.

Messages below the minimum level are silently discarded. All other configuration is automatic — no additional setup is required.

Log Entry Format#

Each log call writes a single JSON object followed by a newline:

{
  "timestamp": "2026-06-17T10:00:00.000+00:00",
  "level": "info",
  "severity": "info",
  "message": "User created",
  "context": {
    "user_id": 42
  }
}

Severity Mapping#

PSR-3 defines eight log levels. The logger maps these to five severity buckets in the severity field, which is intended for use by structured log sinks and alerting pipelines. The original PSR-3 level is always preserved.

meritum/structured-logging builds on this logger to add enrichment, channel routing, and pipeline processing. See the structured-logging guide for details.