How to change form field contents in existing PDF using PHP?

(Probably old issue but I didn't find a posting)

Simple case:
1. I have a PDF file I made with Acrobat PRO. It contains a form with
two fields, "Name" and "TestScore".
2. From my PHP file on linux server I just want to open this PDF file
and change the content of the Name and Testscore form fields.


Could someone show me a simple code example on this?


And what do I need of addons? PDFlib and licences?