Including extra debugging Information in Symfony error log

config.yml

# app/config/config.yml
services:
    monolog.formatter.request:
        class: Monolog\Formatter\LineFormatter
        arguments:
            - "[%%datetime%%] [%%extra.username%%] %%channel%%.%%level_name%%: %%message%% %%context%% [%%extra.postParams%%]\n"

# app/config/config_prod.yml
monolog:
    handlers:
        main:
            type:         fingers_crossed
            action_level: error
            handler:      nested
        nested:
            type:  stream
            path:  "%kernel.logs_dir%/%kernel.environment%.log"
            level: debug
            formatter: monolog.formatter.request
        console:
type: console

ExtraProcessor.php

<?php
namespace AppBundle\Monolog;
use JMS\DiExtraBundle\Annotation as DI;
use Symfony\Component\HttpKernel\Event\GetResponseEvent;
use Symfony\Component\Security\Core\Authentication\Token\Storage\TokenStorageInterface;
use Symfony\Component\Security\Core\User\UserInterface;
/**
 * @DI\Service("app.monolog.extra_processor")
 * @DI\Tag("monolog.processor")
 */
class ExtraProcessor
{
    /**
     * @DI\Inject("security.token_storage")
     *
     * @var TokenStorageInterface
     */
    public $tokenStorage;
    /**
     * @var UserInterface
     */
    private $user;
    /**
     * @var array
     */
    private $postParams;
    /**
     * @param array $record
     *
     * @return array
     */
    public function __invoke(array $record)
    {
        if ($this->user instanceof UserInterface) {
            $record['extra']['user'] = [
                'username' => $this->user->getUsername(),
            ];
        }
        if (null !== $this->postParams) {
            $record['extra']['postParams'] = $this->postParams;
        }
        return $record;
    }
    /**
     * @DI\Observe("kernel.request")
     *
     * @param GetResponseEvent $event
     */
    public function onKernelRequest(GetResponseEvent $event)
    {
        $postParams = $event->getRequest()->request->all();
        if (false === empty($postParams)) {
            $this->postParams = serialize($postParams);
        }
        $token = $this->tokenStorage->getToken();
        if (null === $token) {
            return;
        }
        $user = $token->getUser();
        if (!($user instanceof UserInterface)) {
            return;
        }
        $this->user = $user;
    }
}

From https://dotdev.co/including-extra-debugging-information-in-your-symfony-error-log-1b14ced9efe7#.wj0ub6k7h