This project was done to understand the interaction through websocket between an Ionic application and a PHP server.
The application has been implemented through the rxjs library
If you want to start the client side, that's a Ionic app, you have to type in your prompt, the command ionic serve. For more details check the ionic Doc https://ionicframework.com/docs/cli/serve/
The server app is even simpler than the client-side. You have to type php server.php.