Any way to make my phone lock when I turn screen off?

[baloniman612]

Was wondering if there was something in settings I was missing, or an app that when I turn the screen of my phone off, it would automatically lock, it has a bad habit of unlocking itself in my pocket. Would be nice if it used the same way if you hold the end key (hate to hold it for 5 seconds everytime to lock it) Touchflo 3d unlock, looks very nice.