Forgot passcode?

Hello. I have had my iPhone 4S for the past year. I used to have a passcode on it, but soon it became annoying because I would always have to type it in and I felt like it took too much time.
I switched from the simple to complex passcode around June or so (mainly because all my friends knew my passcode and I couldn't think of a new, creative 4-digit passcode).
After a while, I figured it would be easier to just remove the passcode. No one besides me really uses my phone anyway.
Fast forward three months, and now I've forgotten my passcode and I want to put a new one back up again.
Since I do not know my old passcode, how can I do this?
Is the only way to restore my phone?
Will restoring it require me to input my passcode?
Help please!
Thank you!