Logging with Monolog

Logging

Symfony comes with an outside library - calledMonolog_ - that allows you to create

logs that can be stored in a variety of different places.

Symfony comes with a minimalist `PSR-3`_ logger::class:`Symfony\\Component\\HttpKernel\\Log\\Logger`.

In conformance with `the twelve-factor app methodology`_, it sends messages starting from the

``WARNING`` level to `stderr`_.

The minimal log level can be changed by setting the ``SHELL_VERBOSITY`` environment variable:

``SHELL_VERBOSITY`` value Minimum log level

``-1`` ``ERROR``

``1`` ``NOTICE``

``2`` ``INFO``

``3`` ``DEBUG``

The minimum log level, the default output and the log format can also be changed by

passing the appropriate arguments to the constructor of:class:`Symfony\\Component\\HttpKernel\\Log\\Logger`.

To do so,:ref:`override the "logger" service definition<service-psr4-loader>`.

Logging a Message

To log a message, fetch the ``logger`` service from the container in

your controller::

To log a message, inject the default logger in your controller::

The ``logger`` service has different methods for different logging levels/priorities.

You can configure the logger to do different things based on the *level* of a message

(e.g.:doc:`send an email when an error occurs</logging/monolog_email>`).

SeeLoggerInterface_ for a list of all of the methods on the logger.

Monolog

Symfony integrates seamlessly with `Monolog`_, the most popular PHP logging

library, to create and store log messages in a variety of different places

and trigger various actions.

For instance, using Monolog you can configure the logger to do different things based on the

*level* of a message (e.g.:doc:`send an email when an error occurs</logging/monolog_email>`).

Run this command to install the Monolog based logger before using it:

..code-block::terminal

The following sections assume that Monolog is installed.

Where Logs are Stored

.. _`the twelve-factor app methodology`:https://12factor.net/logs

.. _PSR-3:https://www.php-fig.org/psr/psr-3/

.. _`stderr`:https://en.wikipedia.org/wiki/Standard_streams#Standard_error_(stderr)

.. _Monolog:https://github.com/Seldaek/monolog

.. _LoggerInterface:https://github.com/php-fig/log/blob/master/Psr/Log/LoggerInterface.php

.. _`logrotate`:https://github.com/logrotate/logrotate