Developer manual

Using the logging method

To log something simply call \TYPO3\CMS\Core\Utility\GeneralUtility::devLog(). This method takes the following parameters:

$msg The message that you want to write to the log
$extKey The key of the extension writing to the log

Indication of the severity of the message. The following values are expected:

  • -1 for ok status
  • 0 for a purely informational message
  • 1 for a notice
  • 2 for a warning
  • 3 for a (fatal) error

This parameter is optional and defaults to 0.


This variable can be any type of data that you wish and that you find useful for information or debugging purposes. The Database Writer serializes it before storage in the database.

This parameter is optional and defaults to false.


If you store a lot of stuff in the $dataVar or if you call the “devLog” very frequently, you may end up with a very large “tx_devlog_domain_model|_entry” table in your database. Check it out regularly and don’t hesitate to use the clean up features as the relevant configuration options.

More about severity levels

It may not always be easy to choose a severity level. The descriptions below go into a bit more detail and will – hopefully – make the choice easier.

OK (-1)
These events indicate that everything went fine, no error occurred (at least up to that point where the event was created). No action needs to be taken.
Info (0)
These events are purely informational. They are normally used for debugging purposes only and require no special action.
Notice (1)
Abnormal condition, but not blocking. Notices are meant to raise attention. Processes have been completed, but things are not running as smoothly as they could and the condition should be investigated.
Warning (2)
These events are used to notify significant problems. Processes have been completed, but parts of them may be missing, wrong or corrupted. Warnings should not be ignored and action should definitely be taken.
Error (3)
These events signal that something went fatally wrong. Processes were not completed and action is definitely needed. Alternately this level may be used to point to a failed event, but in a process where failure can be expected, e.g. a login attempt with the wrong password.

Extra information

The devlog extension stores information beyond the parameters passed to the \TYPO3\CMS\Core\Utility\GeneralUtility::devLog() method. Some of it is automatically retrieved, like the id of the currently logged in BE user, if any.

If the devlog call is made in the FE context, the page id will also automatically be retrieved from $GLOBALS['TSFE']->id. This variable is not defined in other contexts, in particular the BE. There is still a way to pass a page id to the devlog, if it makes sense, but you need to set it yourself in the global variable :code:`$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['GLOBAL']['debugData']['pid']. If defined, this variable will be taken into account by the devlog.

All this work happens in the \Devlog\Devlog\Utility\Logger class.

Custom Writers

The data passed in the \TYPO3\CMS\Core\Utility\GeneralUtility::devLog() call is stored by classed called “Writers”. The extension provides two Writers out of the box: one write to the database, the other to a file. It is pretty easy to develop custom Writers.

First you want to create a new class which extends \Devlog\Devlog\Writer\AbstractWriter, which itself implements \Devlog\Devlog\Writer\WriterInterface. The interface defines a single method called write() which should take care of storing each log entry wherever and however it wants.

Once you hace created your writer, register it in your extension’s ext_localconf.php file with the following syntax:

$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['devlog']['writers']['foobar'] = \Foo\Bar\Writer\FooBarWriter::class;

where foobar should be a unique key for your Writer.


It is actually possible to overwrite the default Writers be registrer a different class for keys db (Database Writer) and file (File Writer).

It would also be possible to disable a Writer, by unsetting its entry in the $GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['devlog']['writers'] array.