On Apple iPhone, if you tilt your phone on its side (horizontal), the screen rotates to landscape mode. But if the portrait lock is on, turning the phone in any direction will keep it in portrait orientation. iPhone users of iOS 7 are facing the issue of their screen locked in portrait mode. They are unable to figure out how to unlock the screen so that it can display both portrait or landscape mode as appropriate when the iPhone is held accordingly. The landscape mode is great while you are watching a video or playing game on your phone. Thus, below is how iPhone users can unlock the portrait mode lock.
An orientation lock on the iPhone locks your phone to either portrait mode or landscape mode as required. To unlock portrait mode lock, swipe up from the bottom of the screen to summon control center and toggle the orientation lock in the upper right corner. Its symbol is like an unlocked lock encircled in an arrow. You can apply the orientation lock settings either at the home screen, on the lock screen or in an App.