The recommended way to make changes to the gbl.php file is to re-run the SalesCart-X wizard on the SalesCart website you want to change and select Modify SalesCart settings only. This will automatically create a new gbl.php file and update the gbl.php file on the <root web>.
Warning! Each time you re-run the SalesCart Web wizard, the existing gbl.php file on the <root web> will be renamed and replaced. If the original gbl.php file is important to you, you should back up it up to a different file name.