Startup wants me to switch to PhP and other languages. Please advice.

Hi, so i am a fresher MERN stack developer and I interviewed at a small startup where they want me to first learn the basics of PhP, MySQL, AJAX, JS, jquery, curl. I am very well familiar with JavaScript and MySql, from these and thats it. I want advices, as are these technologies still in demand, or if I go out of the startup will I be getting jobs on the basis of these tech stacks.

TLDR: Is it worth investing time on php, mysql, ajax,jquery, curl for a mern developer.