If your iPhone Power Button is broken, and it’s turned off, it will turn on when the battery starts to charge by connecting it to the PC or Power cord. But if for some reason id doesn’t there seems to be no way tu turn it on…. But it certainy there is a way!
This worked for me, an I have read about some other guys succeding:
Press the Glass in an area below the power button with one finger and other in the back while pushing the powere button. Good Luck!