Kind of interested in this too. I just started redeveloping a php site in codeigniter bringing it from version 2 to 4 and when I first attempted this a year ago, it didn't seem that neovim support wasn't very good for php.. I could be mis-remembering. I keep a nice setup with neovim and tmux which also works great in an i3 environment.

I've basically been just using a basic neovim setup for now (haven't even setup the language servers yet) while wrestling the app back up to speed. But with a neotree and multiple tmux windows for commands, it's still been a pretty fluid.