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In Drupal 7 I use devel's drupal_debug() or its alias dd() to log a variable to a drupal_debug.txt in the site's temp directory.

In the Drupal 8 version of devel this function has disappeared. It seems to be replaced by DevelDumperManagerInterface But it is not clear to me how it used.

How can I log variables to a txt file in Drupal 8?

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  • How about printing them in a message? drupal_set_message(var_dump($variable), 'warning');
    – No Sssweat
    Oct 4, 2016 at 4:21
  • In the D8 devel module drupal_debug() as been replaced by the devel.dumper service, but the alias dd() is still there and now points to the service.
    – 4uk4
    Oct 4, 2016 at 6:47
  • Also printing it to the logs is possible with \Drupal::logger('crimi')->notice($value); but dd() can be nice in some cases. Actually I managed to get it working when I figured out I was disabling the devel module constantly
    – batigolix
    Oct 4, 2016 at 12:27

1 Answer 1

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The DevelDumperManagerInterface interface is implemented by DevelDumperManager. This class is in turn used as a service, 'devel.dumper'.

One way to use this function would be the following:

$ddumper = \Drupal::service('devel.dumper');
$ddumper->debug($variable_name, NULL, 'default');

That would log the variable $variable_name to drupal_debug.txt located in the temp folder directory. See DevelDumperManager::debug() docs for more information.

Good luck!

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6
  • What exactly does this code do? does it dump the variables somewhere on the page when the code runs?
    – No Sssweat
    Oct 4, 2016 at 4:25
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    @NoSssweat : It logs a variable to a drupal_debug.txt in the temp folder directory. See api.drupal.org/api/devel/src%21DevelDumperManager.php/function/…
    – Stefanos Petrakis
    Oct 4, 2016 at 7:03
  • I think I am missing something here. I get the error exception 'Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException' with message 'You have requested a non-existent service. I run this code from within a migrate plugin, so the devel functions may not be availabe at that point ...
    – batigolix
    Oct 4, 2016 at 10:12
  • In that case, please update your OP to add this important information. I am gonna take a look at this and update my answer accordingly.
    – Stefanos Petrakis
    Oct 4, 2016 at 10:59
  • First question: Is the devel module installed and functioning in your Drupal instance? For example, what do you get for this command: drupal container:debug | grep debug.dumper ? Or for this one (using drush): drush ev "\Drupal::service('devel.dumper');"
    – Stefanos Petrakis
    Oct 4, 2016 at 11:08

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