how to write " file download" program

[bin cai <bc...@yahoo.com>]

Hi,
I am afraid to ask some instruction for my work.
I am thinking to write a program to help client to download some sound file from server.
Client send request to download a file in server. The request includes the file name and directory he want the file to be loaded onto. the request invokes the "download" program callled for example as "download.php"  in server.(Apache). The download.php retrieve the sound file (greeting.wav) and download the file to client.
 
Besides. i need to wirte a upload program called "upload.php" help client to upload file from client to server.
 
Any help will be really appreciated. 


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