Advanced: Logging

Erlenmeyer includes a flexible logging system designed for both file-based and console-based environments.
It provides standardized severity levels and supports context-aware exception logging, including request details and stack traces.

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Overview

Logging in Erlenmeyer is powered by the LoggerInterface, which defines two main methods:

public function log(LogLevel $level, string $message): void;
public function logException(Exception $e, ?Request $request = null): void;

Two implementations are included by default:

Class	Description
FileLogger	Writes structured log entries to disk, with automatic rotation.
ConsoleLogger	Writes log entries to the PHP error log or STDERR (useful in CLI/testing).

You can also create custom loggers by implementing LoggerInterface — covered in the Custom Handlers section.

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Log Levels

Erlenmeyer defines standard log severity levels using the LogLevel enum:

enum LogLevel: string {
    case DEBUG = 'DEBUG';
    case INFO = 'INFO';
    case WARNING = 'WARNING';
    case ERROR = 'ERROR';
    case CRITICAL = 'CRITICAL';
}

All loggers support these levels consistently.

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1. FileLogger

Basic Setup

The FileLogger stores logs in a directory of your choice and automatically rotates log files when they reach 3MB.

use AdaiasMagdiel\Erlenmeyer\Logging\FileLogger;
use AdaiasMagdiel\Erlenmeyer\App;

$logger = new FileLogger(__DIR__ . '/logs');
$app = new App(null, $logger);

• Logs are stored in info.log inside the specified directory.
• When info.log exceeds 3MB, it is renamed to info.log.1, and older logs are shifted up to info.log.5.

Example Log Entry

[2025-10-15 14:03:21] [INFO] Route registered: GET /users

Exception Logging

Exceptions are logged with full context, including the request method, URI, and stack trace:

[2025-10-15 14:05:11] [ERROR] Invalid argument in /app/UserController.php:84
Request: POST /users
#0 /app/App.php(210): ...

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2. ConsoleLogger

The ConsoleLogger writes directly to PHP’s error log or STDERR. This is ideal for development, testing, or containerized deployments.

use AdaiasMagdiel\Erlenmeyer\Logging\ConsoleLogger;

$logger = new ConsoleLogger();
$app = new App(null, $logger);

You can also exclude specific levels to reduce verbosity:

use AdaiasMagdiel\Erlenmeyer\Logging\LogLevel;

$logger = new ConsoleLogger([LogLevel::DEBUG, LogLevel::INFO]);

Now only warnings, errors, and critical messages will appear in your logs.

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3. Custom Logger Injection

Any logger implementing LoggerInterface can be injected into the application.

use AdaiasMagdiel\Erlenmeyer\App;
use MyApp\CustomLogger;

$logger = new CustomLogger();
$app = new App(null, $logger);

The logger is used internally by the App to record:

• Route registration and middleware execution
• 404 and 500 errors
• Unhandled exceptions
• Asset serving and redirect handling

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4. Handling Exceptions Manually

You can also log exceptions directly in your route handlers or middlewares:

use AdaiasMagdiel\Erlenmeyer\Logging\LogLevel;

$app->get('/users', function ($req, $res) use ($app) {
    try {
        // ...
    } catch (Exception $e) {
        $appLogger = new FileLogger(__DIR__ . '/logs');
        $appLogger->logException($e, $req);
        $res->setStatusCode(500)->withText('An internal error occurred');
    }
});

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5. When Logging is Disabled

If you initialize FileLogger without a directory path:

$logger = new FileLogger('');

Logging is silently disabled — no files are created, and all log calls become no-ops.

This can be useful for production builds where logs are handled by external systems.

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Summary

Logger	Output	Rotation	Contextual Exceptions	Recommended For
FileLogger	Files (info.log)	✅ Yes	✅ Yes	Production
ConsoleLogger	error_log() / STDERR	❌ No	✅ Yes	Development / CI
Custom Logger	User-defined	Optional	Optional	Advanced setups

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Next: 📘 Custom Handlers →