Hey @Stefan,
Sorry, I think I misunderstood the question. If you are looking for a front end for data entry and configuration, something along the lines of this:
If that is the case, I would recommend that you take a look at Strapi. I have used it in the past to create the front end interface for a number of different purposes. Web apps, new UI for old applications, data entry, websites…these are all possible with Strapi.
Essentially, you could use Strapi to build the “behind the scenes” interface, point n8n at the data store which you have created to support Strapi, and then n8n would build out and push data/information to the php web server.
Also, take a look at @smamudhan’s excellent article:
They specifically talk about using Strapi along with n8n.
I hope that points you in the rights direction!