Read a text file and echo something if text exists?

[ChrisMartino]

Hello, I am trying to make it so when you enter a new line in a text file like this format:

ThisIsPlayersName 127.0.0.1

If the text you entered into the textbox matches either the IP or ThisIsPlayerName it echos the players name matching the ip, when it reads the text file it would be on a webhost e.g

www.example.com/banlist.txt

Could anybody help me do this?, Thanks.