BUNN1E5

I want to to check if a person who comes to my site is either new or recurring and allow a download ONLY if they are new to the site. I would like to do something like check the IP adress of the person and see if it is in the database. I have never programmed in php before so it is entirely new to me, so i would like you to help me by writing an example script that does this that i can modify. Thank You