What to learn in addition to PHP / JQuery web developer?

Question

PHP

Hello, I am an experienced web developer, I work for myself, I mainly write in PHP+MySQL (backend) and HTML+JQuery+CSS/SCSS (frontend). The main part of development under WordPress (plugins and themes), additional - the development of custom systems (specialized CMS for specific needs from scratch). I mostly work alone (without a team), so it is not necessary that the technology be convenient for team development. Customers - abroad (I do not work with Russia). I work on Macs (if that matters).
Question - I understand that with these technologies I'm probably already in the Stone Age (although they fit perfectly for my tasks, and I earn very well and my customers are satisfied). Tell me what else I should learn from the current demand to make my work more efficient, productive, and interesting, or to expand the capabilities of PHP and JQuery? Add new features to your developments? Thank you!

Answer 1

I found an interesting infographic that will help both me and others decide what else is worth learning:

Answer 2

get acquainted with frameworks, you can start with micro, slim or silex, and then try a full-fledged one: laravel, symfony, yii.
on the vue or react front, along with webpack.

Answer 3

Do not interfere with the head to work and earn money.
When a task appears that is impossible with the help of tools familiar to you, then you will learn something new.
And to improve the skill, I would recommend:
For backing - Python and Node.
To the front - Webpack.
For mobile - PhoneGap.

Answer 4

If you want to stay in the WordPress niche and develop further with possible growth and money - vanilla JavaScript and modern practices in it, React (because Gutenberg). And, of course, more correct PHP.

Answer 5

The WP developer market is crowded. My opinion is that you need to look towards frameworks.