Create a digitally / electronically signed HTML form using php

Question

I am looking for a solution to add a signature to a form. One where someone can sign with a mouse or finger on a touch device. I am wondering if I can use something like jSignature https://willowsystems.imtqy.com/jSignature/#/about/ to create an image, process the form using php and create a PDF file and then add the image to the PDF.

I studied a little and did not find a clear solution for this. Basically, I want to create a simple contract for a freelancer that customers will sign on the Internet.