implementing downloads with php?

Hi; This is new territory for me a maybe a bit off topic but I am interested in finding out how to implement a downloading mechanism with php and without using ftp (if possible). I am understanding that http has a 'put' command. Is this the clue? When a file is downloaded from a site, like, for instance, a source code file from a directory. If the user does not have an ftp client, does the browser negotiate an ftp connection? As an application this could be used for file transfer via a web site. Thanks for time and attention JK