I've successfully uploaded the file to my php server.
However, sending extra information to the server does not work.
My code is as follows:
conn.setRequestProperty(Config.KEY_COURSE_TITLE, course_title);// trying to send course_title (a string variable) to php server
$course_title= $_POST['course_title']; // trying to access sent data
Full code: http://paste.ubuntu.com/15358822/