I uploaded the script into public_html folder, but when i visit the site, Firefox asked me:
"You have chosen to open:
which is: application/x-httpd-php (536bytes)
from http://23.239.30.153
What should Firefox do with this file?"
Open with:.....
Or Save ....."
So I tried to pass it by direct to instal folder. This time I received another message:
500 Internal Server Error.
So please help to fix this, thanks

Regards,

$ wget -S -O - http://23.239.30.153/
--21:14:35--  http://23.239.30.153/
           => `-'
Connecting to 23.239.30.153:80... connected.
HTTP request sent, awaiting response...
  HTTP/1.1 302 Found
  Date: Wed, 05 Nov 2014 02:14:35 GMT
  Server: Apache/2.4.10 (Ubuntu)
  Location: /install/
  Content-Length: 0
  Keep-Alive: timeout=5, max=100
  Connection: Keep-Alive
  Content-Type: text/html
[snip]

On your system, Apache currently does not know that PHP files are to be treated specially. See the guide for installing PHP; this works for Apache on Ubuntu.