php - Get data from a server with Objective-C -

I am trying to create an information system between a PHP server and an iOS device, such as in the Facebook app.

I already know how to request a PHP via GET or Post and wait for the response. But I would like to get the server's response without any request, is it possible? Or should I make a request in every x second?

Keeping in mind (APNS). You send a message to the APNS server, and the server sends a notification to the device (device) you specify. This is standard practice for apps like Facebook.

When a device receives a notification, it sends it to the app (if the app is running) or alerts the user (if not it). The user can choose to start the app, on which notification notification is issued. The app can then contact your server to update your information or update.