Most people, including myself feel they are in over their head when starting out with PHP.
The approach I tend to make is firstly understand what I want to happen (The data model).
Second try to find examples on the net (Google Search) of open source projects or solutions others have created to help the community learn PHP.
It is very easy to use others code but I have fallen over many times because I didn't understand the basic principles of PHP.
My advice to you is this:
Search for examples of simple form processing. I already gave you an example in the post above. Once you have the basics you can build on that with your own design to fit your data model.
If and once you have tried to put something together and you are maybe having difficulty with some code, then post it in this forum and I am sure people will be glad to help you, as they have with me.
Good luck and hope to see you on the forums real soon 🙂