well basically client comes to my site and decides to download my product say my forum so in stead of downloading all the files he downloads a setup.php file and uploads to his server once he runs setup.php it goes to my site and begins to download all the file to clients server
1) client goes to my site and decides to download script
2) downloads a single php file and places that file on his/her server
3) runs the php file on his server and script goes to my server and downloads the entire script straight to clients server
4) client has all files required to install and run script
You would have to read the files from your server (PHP: readfile - Manual) and write them to theirs (PHP: fwrite - Manual). This would present a problem when you try to transfer over large files like images, it would take a very long time.
I dont see any possible advantage in this method over giving them all the files to download.