> For the complete documentation index, see [llms.txt](https://quantumphp.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://quantumphp.gitbook.io/docs/packages/logger/overview.md).

# Overview

The Logger package gives Quantum a small PSR-3-compatible logging layer with three delivery modes:

* write to one file
* write to a date-based daily file
* send messages to the DebugBar message store during debug mode

Use it when you want framework-level logging through `logger()` or the global level helpers, while keeping the output backend configurable.

## When to use it

Reach for Logger when you need to:

* record application errors or warnings to disk
* switch between a single log file and one file per day
* surface debug messages inside Quantum's debugger instead of writing files

If you only need a raw filesystem append, use Storage directly. Logger is useful when you want severity filtering and adapter selection.

## Package shape

The package is built from a few small parts:

* `Quantum\Logger\Logger` is the PSR-3 logger users call
* `Quantum\Logger\Factories\LoggerFactory` resolves and caches logger instances by adapter name
* adapters implement `Quantum\Logger\Contracts\ReportableInterface`
* `Quantum\Logger\LoggerConfig` holds the active severity threshold map
* helper functions expose the common entry points globally

## Adapter model

Logger supports these adapter names:

* `single`
* `daily`
* `message`

In normal runtime, the factory uses the requested adapter or the configured default.

In debug mode, the factory always resolves the `message` adapter instead. That means debug runs send logs to the debugger message store, not to file-based adapters.

## Severity filtering

The package compares levels with this built-in order:

* `debug` = 100
* `info` = 200
* `notice` = 250
* `warning` = 300
* `error` = 400
* `critical` = 500
* `alert` = 550
* `emergency` = 600

The default threshold is `error`.

Outside debug mode, a message is reported only when its severity is greater than or equal to the current application threshold.

In debug mode, `Logger::log()` bypasses threshold filtering and reports every call.

## Important constraints

* The active log threshold is stored in static `LoggerConfig` state, so resolving a logger updates process-wide logging behavior.
* `LoggerFactory` caches one `Logger` instance per adapter name inside the factory service.
* The `message` adapter is not available outside debug mode.
* File adapters only use the `trace` context key for output formatting. Other context values are ignored by file logging.
* The package does not validate arbitrary custom level strings. Stick to standard PSR log levels for predictable filtering and output.
* The `daily` adapter picks its `<YYYY-MM-DD>.log` file when the adapter is created. In long-running workers, recreate/re-resolve the logger after midnight if you need strict daily rollover.


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