I call PHP the backend toolbox of the Web. It's what I've used, and am using, to develop all the server-side control scripts on this site
I use Javascript as my client-side (in your browser) scripting, and PHP as my server-side (on my server) scripting. You can read more about this on my Code page.
You can find a good general introduction to PHP scripting at PHP.info.
W3 Schools provides another introduction, but also includes more detailed information about PHP scripting as well.
M.D.J. 2021/07/20