IdeaVim is a popular plugin that adds vim shortcuts (e.g. hjkl navigation) to PhpStorm and similar products.
A rare bug Mac users may replicate one day: it’s possible to accidentally disable IdeaVim by pressing cmd-alt-V – the same shortcut as moving files in Finder. PhpStorm does need to have focus; in my case I was typing the standard copy/paste/move shortcuts to transfer some files in the Project window.
You can see/toggle the Vim status with Tools > Vim Emulator (which won’t show up as a search result if you use shift-cmd-A and type ‘ideavim’). It’s a handy shortcut to be aware of – temporarily turning Vim off may make it easier to complete certain refactoring tasks where you’re entering a new variable name.
IdeaVim’s settings are in vim_settings.xml in the WebIde100 folder (where the 100 at the end indicates version 10.0.*), in the event of a problem you can inspect or trash that file.