If it’s been days (or even weeks) since you’ve rebooted your Apple iPhone, you may notice that its performance decreases over that time. The screen itself may actually freeze and become unresponsive, no matter where you touch it. If this occurs, you can still turn off your iPhone and turn it back on by performing a “hard reboot” which forces the device to shut down, no matter what. Writer Bio

How to Turn Off an iPhone When the Screen Freezes - 10