iOS 9 allows blocking the orientation of the screen using the Mute button, this option being available in the past only for iPad tablets, but the Apple company decided that even owners of iPhone terminals should benefit from it. In the image above you can see what the new function looks like, it is available for control in Settings > General > Use the side switch for : , Settings > General.
By choosing the option Lock rotation or Mute mode, you will use the Mute side button of the iPhone terminals for any of the two functions, its action and performing the desired operation. Considering that in the Control Center, there is still a button to lock the screen orientation, offering a separate option for the Mute button is not very logical.
Despite this, the way it is presented makes it clear that the implementation is not final, so it remains to be seen if it will also be found in future versions of iOS 9.
