Craft\AmForms_SubmissionsController::_uploadFile PHP Method

    private function _uploadFile($file, $folderId)
    {
        $fileName = AssetsHelper::cleanAssetName($file['name']);
        // Save the file to a temp location and pass this on to the source type implementation
        $filePath = AssetsHelper::getTempFilePath(IOHelper::getExtension($fileName));
        move_uploaded_file($file['tmp_name'], $filePath);
        $response = craft()->assets->insertFileByLocalPath($filePath, $fileName, $folderId);
        // Make sure the file is removed.
        IOHelper::deleteFile($filePath, true);
        // Prevent sensitive information leak. Just in case.
        $response->deleteDataItem('filePath');
        // Return file ID
        return $response->getDataItem('fileId');
    }