This is more or less a note, when my brain takes a vacation.
I have a form, where the user could select one or several lines from either the right or left boxes.
This is a part of html code (actually PHP), remember to have [ ], this indicates a array. The user could select just one, or several.
In my form handler (in a Docker container, communicate with SendGrid), I use implode to convert the array to string.
It will handle the data and process the data to sql, updating MYSQL database in another Docker container, after that it will send a email with the data.