Submit to a txt file

I hope this is pretty easy. Im a noob so I really dont know.
I need a script so that I have an input area. Then I have a .txt file. When someone submits, whatever is typed in the input gets added as a new line in the txt file.

Google is your friend! http://www.tizag.com/phpT/filewrite.php

Good luck!

That looks like its what I need. I'm going to try it out now. Thanks.