Mirroring from my iPhone 7+ to aucary projector wirelessly to wall
Two options you have to connect your iPhone to a projector.
Option 1) Get an Apple TV and connect that to the projector using a simple HDMI cable on either end. Then use airplay to stream the content of your iPhone to the Apple TV. I personally like this option as then you have a smart projector with plenty of options for playing content without your phone or computer.
Option 2) Get an Apple Lightning Digital AV Adapter, which then plugs into your iPhone's lightning port and gives you an HDMI port. From there you can take a simple HDMI cable from the adapter into the projector.
Cost is cheaper on the lightning digital av adapter ($49 USD vs $149-179 USD) however long term you might find having an Apple TV more useful than the adapter.