You don't need a debugger, just like you don't need a windshield. It's just about that critical. While you can build applications without this heads-up display, it's going to take a lot more time.
What is Xdebug? Xdebug provides insight into how your PHP application executes. You can pause the execution. You can examine variables. You can review the methods and functions executed to get to this place. You can even execute code on the fly.
I want to help you become an effective developer. Part of this comes through mastering Xdebug. I will show you how to do this.