Press and hold the side button and either volume button until the power-off slider appears
Drag the slider to turn off the iPhone
If the iPhone has a Home button, press and hold the side button or top button until the power-off slider appears
Drag the slider to turn off the iPhone
If the screen is unresponsive, press and quickly release the volume up button
Press and quickly release the volume down button
Press and hold the side button until the Apple logo appears, then release it to restart, or continue holding until the device powers off if supported by the model