@kpollock it' not you. Yes, it should seem obvious that the language should be installed manually or separately, so you should have gotten that part, sorry. But no, there doesn't seem to be information anywhere about defining the underpinnings. This "understanding" seems to be left to the individual through research as you're doing.
After I installed PHP I manually set my environment PATH to include the PHP folder. OR in VS Code you can go to menu>File>Preferences>User Settings, the settings are maintained as a JSON object (unlike VS) and there is a PHP section for the .exe path.
Since you mentioned Node, you may not have installed Node.js manually. (I don't know if Node comes with VS Code either.) It might have come in with a VS2015 extension like Gulp or some other higher-level functionality, or maybe it was an installation option with VSC. If you can't use node or npm from a console, set your environment PATH to include it.