Which porgramming language should i learn as a back end developer [on hold]

I'm programming as a hobby (in my free time, I go to school) and next year I will graduate. I want to become a backend web developer after school (either go to university or do an apprenticeship). I know the basics of HTML and CSS and recently started learning some PHP and mysqli so, I can make my websites more interactive (backend stuff). I can build a login system and some other stuff with php but I'm really not an expert at all at php. Now I heard on some websites that js would be much better to learn instead of php. Should i learn js instead of wasting my time on PHP? And what about frameworks? Thanks in advance