What to learn to create dynamic user controlled web page/app

So you know little about programming but you want to build complicated applications. You've got a lot of work to do, it can be done but it will take you time, a lot of frustration and to be honest...you'll probably give up. That is unless you truly want to learn and be good at programming.

So to answer your question, if what you want to do is in that link, then all you need is a javascript library (or you can roll your own if you are brave) such as jQuery or Mootools. To implement that link, all you need is javascript. To make it persist and save selections per user, that is where you need a server side language and a data layer (PHP and MySQL).

PHP and Ruby serve the same purpose in your instance. Both are considered server side in what you want to do. Pick one and go with it. PHP typically has a lower barrier to entry but really...figure out which one you like and run with it. I started with PHP...doesn't mean i liked it.

The other issue you need to address is being able to take a huge application and break it down into smaller pieces. If you can't do this, you will get discouraged and abandon your project, I guarantee it. Since you are new, don't look at this as implementing a shopping cart, break it down into pieces. You don't know how to code that well to begin with so the first thing you need to conquer is rendering something from mysql on a web page. So start there, learn how to connect to mysql from PHP. Then learn how to execute a sql query. Then learn how to display the sql query results using PHP in your HTML. It will take a while, but next thing you know you'll have half the functionality you need based on your sample link and you may have learned a few tricks along the way.

You mention that you thought about using zencart but you've chosen to try and create your own shopping cart. That right there is typical new developer mistake. Why are you reinventing the wheel? You are just going to create a buggy piece of software. Using Zencart (or an equivalent) you are selecting a battle tested piece of software that may still have issues, but it won't have issues like you would if you write it from scratch. There is an argument for build vrs "buy" but in your case, if this is going to be used in a production environment and given what little i know about your skills, I would recommend "buy" rather than build for you.

The last tidbit I'll share is that if you tackle this project with little knowledge of programming with the idea you are going to create a shopping cart like functionality in a short amount of time you are setting yourself up for failure.