Order.php

<?php
namespace modules\appmodule\behaviors;

use Craft;
use craft\elements\Entry;
use craft\events\ModelEvent;
use craft\helpers\ElementHelper;
use yii\base\Behavior;

class Order extends Behavior
{
    public function events()
    {
        return [
            Entry::EVENT_BEFORE_SAVE => function (ModelEvent $event) {
                $entry = $event->sender;

                if (ElementHelper::isDraftOrRevision($entry)) {
                    return null;
                }

                // …do something before save: doesn't work
            },
            Entry::EVENT_AFTER_SAVE => function (ModelEvent $event) {
                $entry = $event->sender;

                if (!$event->isNew || ElementHelper::isDraftOrRevision($entry)) {
                    return null;
                }

                // …do something after save: it works
            },
        ];
    }
}