mdm\upload\UploadBehavior::saveUploadedFile PHP Method

    public function saveUploadedFile($deleteOldFile = null)
    {
        /* @var $file UploadedFile */
        $file = $this->{$this->attribute};
        if ($file !== null) {
            $callback = $this->saveCallback;
            if ($callback !== null && is_string($callback)) {
                $callback = [$this->owner, $callback];
            }
            $model = FileModel::saveAs($file, ['uploadPath' => $this->uploadPath, 'directoryLevel' => $this->directoryLevel, 'saveCallback' => $callback]);
            if ($model) {
                if ($this->savedAttribute !== null) {
                    if ($deleteOldFile === null) {
                        $deleteOldFile = $this->deleteOldFile;
                    }
                    $oldId = $this->owner->{$this->savedAttribute};
                    $this->owner->{$this->savedAttribute} = $model->id;
                    if ($deleteOldFile && ($oldModel = FileModel::findOne($oldId)) !== null) {
                        return $oldModel->delete();
                    }
                }
                return true;
            }
            return false;
        }
    }