Thanks to the latest update for the PlayStation 4 and the addition of an officially supported app in the Apple App Store, the PS4's Remote Play is now available on compatible iOS devices. However, since iOS doesn't natively support the PS4's DualShock 4 controllers, gamers will have to resort to on-screen controls or a supported third-party solution.
https://www.notebookcheck.net/Latest-PlayStation-4-update-brings-Remote-Play-support-to-iOS-devices.413711.0.html