Will my cheap iPhone charger from Amazon ruin my phone?

I just got an iPhone charger that wasn't apple brand on Amazon for cheap. People are telling me that it isn't going to work or it will eventually start to ruin my phone. I just recently got an iPhone 5 too so I have no interest in having to buy a new one because the charger is going to ruin it. Will the things people keep telling me really happen?

No. A charger works, or it doesn't. Quit listening to people that don't know what they're talking about.

Depends on who you got it from