file upload is not saving the data

Hello,

I have tried to save file upload by the hook according to the documentation,
which Is not working, please check the below code

function md_gform_after_submission_17( $entry, $form ) {

  $upload_path = GFFormsModel::get_upload_path( $entry[ 'form_id' ] );
  $upload_url = GFFormsModel::get_upload_url( $entry[ 'form_id' ] );

  $filename = str_replace( $upload_url, $upload_path, $entry[ '8' ] );
 

}
add_action( 'gform_after_submission_17', 'md_gform_after_submission_17', 10, 2 );