Auto update feature from PHP app - like antivirus definitions

Hi, Has anyone ever tried to produce an auto-update feature for your PHP application? Say a client downloads version 1, and a month later version 1.1 is available, which makes changes to a few scripts say, add_user.php, modify_user.php and display_users.php Does anyone have a method or way in which these scripts (say the source is available from the project homepage via a URL - something like http://theproject/updates/version1.1/add_user.php.gz) can be downloaded and replace the current one on the client's server? Just theory or a finger to point me in a general direction would be great. Hope this makes sense. Thanks Terence