php upload file for conversion on own server

I am trying to create a page where I can upload a file (happens tone html) and convert it.
This is a workaround for an app that produces a report as and HTML file and I want it as a PDF. The reason to do it on my own server is so that I can add formatting for the same report but different users.

Are there any examples someone could point me to or the code I need to use?