What is the best way to implement a single iframe form?

Question

PHP

Good afternoon, there is such a task.
There will be several mini-sites with several fields to fill in (online receipt of results according to the entered data, the form is the same everywhere). I would like to add / delete / change all these fields at the same time on all sites, and not on each one separately. I think that it is necessary to make one site where this form will lie, and the rest will take it from this site. So what is the best way to implement this? Should I use a regular iframe or is there a more robust solution? Thanks in advance for your reply!

Answer 1

1 server, 1 database - several minisites. Everything works through 1 controller.