Incorrect generation of the order of preprocessing steps

protected function createItemPreprocessing(array $items) {
                $item_preproc = [];
                $step = 1;
 
                foreach ($items as $item) {
                        if (array_key_exists('preprocessing', $item)) {
                                foreach ($item['preprocessing'] as $preprocessing) {
                                        $item_preproc[] = [
                                                'itemid' => $item['itemid'],
                                                'step' => $step++,
                                                'type' => $preprocessing['type'],
                                                'params' => $preprocessing['params']
                                        ];
                                }
                        }
                }