Well, part of it is that PHP was initially one of only a few options, and since then new languages and technologies like Node have appeared and slowly eroded that market share by the simple fact that they are competition. Node became popular for the many good qualities it has: isomorphism, simplicity, etc., and I don't think php devs in particular moved to node as much as devs in general gravitated toward it.
If you look at PHP vs Node in Google Trends, you can see the PHP decline was well on its way before Node.js came on the scene in 2009.
I used to love PHP, but these days JS is good enough that I don't feel the need to look back. My personal JS projects still look PHP-ish in the sense that they're very simplistic, often lacking a build step and often even lacking a framework. I do like having more control over the server logic than what I remember having with PHP (granted this was the days of WAMP and LAMP, and I hear with docker and nginx things are nicer now). I also like the fact that I can go to a single place (npmjs) for both my browser-side and server-side libs because sometimes I haven't decided yet where it'll reside.
If you look at PHP vs Node in Google Trends, you can see the PHP decline was well on its way before Node.js came on the scene in 2009.
I used to love PHP, but these days JS is good enough that I don't feel the need to look back. My personal JS projects still look PHP-ish in the sense that they're very simplistic, often lacking a build step and often even lacking a framework. I do like having more control over the server logic than what I remember having with PHP (granted this was the days of WAMP and LAMP, and I hear with docker and nginx things are nicer now). I also like the fact that I can go to a single place (npmjs) for both my browser-side and server-side libs because sometimes I haven't decided yet where it'll reside.