CakePHP3.x : Save simple audit trails (userIDs) on insert/update

AuditBehavior.php

<?php
/**
 * for CakePHP 3.x
 * Activate this behavior on your models to set values (user ID) to "created_by" and "modified_by" columns on insert/update.
 * see http://book.cakephp.org/3.0/en/orm/behaviors.html#using-behaviors
 * 
 * Please note that if you use such models from Shells(CLI), these values will be set to null.
 * 
 * You also have to set static property "sessionUserID" on AppController::initialize().
 */
namespace App\Model\Behavior;

use Cake\ORM\Behavior;
use App\Controller\AppController;

use Cake\Event\Event;
use Cake\ORM\Entity;
use Cake\Log\Log;

class AuditBehavior extends Behavior
{

	public function beforeSave(Event $event, Entity $entity)
	{
		$sessionUserID = AppController::$sessionUserID;
		
		if(empty($entity->id)) {
			//Log::debug('is going to insert');
			$entity->created_by = $sessionUserID;
		}
		else {
			//Log::debug('is going to update');
		}
		$entity->modified_by = $sessionUserID;
	}
}

AppController.php

<?php
class AppController extends Controller
{
    public static $sessionUserID = null;
    public function initialize()
    {
        parent::initialize();
        self::$sessionUserID = $this->Auth->user('id');
    }
}