Amateur programmer looking to turn an idea into a website

I mostly work with Python and R, but I'm looking to turn a recent project in R into a website using D3.js, JQuery and PHP to accomplish what I was using shiny for previously - I think. I'm completely new to web development, and I want to make sure I'm at least in the right ballpark with my plan before I start working on it.

My R Script (feel free to try it out here, it's definitely a WIP) is fairly straightforward, essentially it takes data from Spotify's API to find related artists and create a graph where each node represents an artist and each edge is a connection between two artists (one appears on the other's related list). To convert this script into a website, it looks like I'm going to have to learn a few new languages.

• For backend, it seems like PHP is the way to run scripts server-side that can then pass information to the client. Is this true? I can't imagine one can run a script in HTML or Javascript... Does PHP talk to Javascript? Like could I create a graph like this one and run a PHP script to query the Spotify API every time a user moused over a node?
• For the front end, it seems like what I want to do is make a website that has super minimal HTML & CSS, as most of the site should be the graph. Does that seem right? I'm reading that the more Javascript a site utilizes, the more it tends to slow down on the client side. Could that be an issue?

Sorry if these seem like dumb questions, like I said I have virtually no idea how to build a website, I want to know if this is how I should get started on learning.