HTTP based uploading using PHP

Revision 1
Hi, I want to upload a PDF file to server where a php script is running. I am new to PHP have no idea how to write this script. I cann't use FTP uploading. I have to use HTTP based uploading.
More clarification:
Upload will be done by C++ (I can do that)
Receive will be done in PHP script(Need help here)
Can any one help?

Thanks