Error with mkdir(): No such file or directory

hi i wanna make some file directory for my image file but i got error
mkdir(): No such file or directory

 public function save($runValidation = true, $attributeNames = null)
    {
        if ($this->imageFile) {
            $this->image = Yii::getAlias('@frontend/web/storage/products/' . Yii::$app->security->generateRandomString() . '/' . $this->imageFile->name);
        }

        $transaction = Yii::$app->db->beginTransaction();
        $ok = parent::save($runValidation, $attributeNames);

        if ($ok && $this->imageFile) {
            $fullPath = Yii::getAlias('@frontend/web/storage' . $this->image);
            $dir = dirname($fullPath);
            if (!FileHelper::createDirectory($dir) | !$this->imageFile->saveAs($fullPath)) {
                $transaction->rollBack();


                return false;
            }
        }

What’s in the $dir?