I've heard PHP is very popular in the freelance world. I don't know PHP. However, I'm sure it wouldn't be difficult to learn since it has many similarities with Java (OOP). It seems to me that Laravel has similarities with Spring Boot (it's MVC and OOP). Also, people say Laravel works well with Vue.js, which is my favorite JS framework.
The projects I would like to work on are custom web applications/websites for small businesses. I have developed custom ERPs before and found that Java was a good fit, except for it taking a long time to develop. I cannot make a choice, and I am constantly switching between trying PHP and Node.js/Express. Any real-world advice would be welcome! I would love to find a stack that I enjoy while doing meaningful freelance coding.
Hi Eva, As you have solid experience with Spring already, you should jump into freelancing with that. It would be quite stressful to start freelancing with a tech stack you don't know well. Then in the background you can keep learning/practicing an alternative and switch over when you are confident enough (eg. 0.5-1 year later). I think you should learn Laravel as you already like it and find it easier. Express has better performance but that is not required for most of the small freelancer projects.
I think Patrik and Alex are right: if you're comfortable with Spring Boot already, you'll be more productive right from the start.
If you wish to learn something else besides, both Laravel and Express are good choices. They aren't in the same category of frameworks: Laravel is an all-in-one solution, while Express is more like "build your own stack from different parts". Which implies that you can use whatever you want as a database engine: MySQL or PostgreSQL are perfectly valid choices (in my school, we teach Express with MySQL, because SQL is still a big thing here in France, and a sought-after skill). You can use Sequelize or TypeORM which support all major SQL DBMS.
Bottom line: using a stack tech, that you enjoy and are comfortable with, matters. Spring Boot + Vue.js seem perfectly fine to me. But do forget jQuery if you're using Vue.js, React or Angular, because it will definitely bring more harm than good!