What's more important for back-end development?

Question

Ruby, Python, PHP or JavaScript?

Answer 1

In web development for back end use=PHP and JavaScript.
In other like games,machine learning,android,AI for back-end use=Ruby and python.

Answer 2

PHP and python are the most used. I don't know if the others are used.
I suggest PHP

Answer 3

Basically used a PHP because PHP was created by idlers who didn't want learn Python, Ruby and JavaScript :))