Apple iPhones are more and more powerful and now capable of being used as a media station to run your home theatre. The easiest way to connect an iPhone is with a basic cable adapter to HDMI. For iPhone models 14 and older they use what is called the Lightning connector. iPhone 15 and onwards are using USB-C. Something to look out for when selecting the projector is to make sure it has an audio output (ARC, 3.5mm audio, or SPDIF) or decent inbuilt speakers.
To connect a projector and iPhone wirelessly you can use an Apple wireless system called AirPlay. Inbuilt into your iPhone or iPhone Pro Max AirPlay is as simple as a few clicks on your phone to connect. Some new projectors come with AirPlay connectivity inbuilt but if you have one that does not have it inbuilt you can easily add it in with the Apple TV box.