What computer script goes good along with html?

If you're asking what to learn next, I recommend JavaScript. It's very useful for a variety of projects, and it can reduce load time nicely.

PHP is good, and I'd suggest that after JavaScript.

(I know just enough code to be dangerous, but my son builds corporate websites for a living. I had a similar discussion with him about a month ago, and it's the basis of my recommendations.)

Many professionals would suggest the opposite. However, it really depends on what you're good at. Neither JavaScript or PHP are really similar to HTML, since both are programming languages. JavaScript is definitely more quirky in nature, since it depends on the browser for its existence, which means a balancing act of compatibility.

Since PHP always has the same environment, on the server, it is more stable.

What I usually recommend to people, is that if you are really good at CSS first, study JavaScript. If you know CSS, but it is not your best skill, go for PHP, because it will still be useful to you. Either way, you may want to explore a little of both, to see which one suits you more.

I learned PHP before I started studying JavaScript, and in the end, I became more of a front-end specialist with HTML/CSS/JavaScript/jQuery. However, I had prior programming experience before I started studying web-development. For you, it is probably different.