If the file is on the local machine, use
include("$DOCUMENT_ROOT/rate/rate.inc.php");
If the file is remote, read the following from the documentation:
If the include()ed file is called via HTTP using the fopen wrappers, and if the target server interprets the target file as PHP code, variables
may be passed to the include()ed file using an URL request string as used with HTTP GET. This is not strictly speaking the same thing as
include()ing the file and having it inherit the parent file's variable scope; the script is actually being run on the remote server and the result is
then being included into the local script.