The script has an error which you also have (copied and pasted from source), being the missing semi-colon at the end of:
require("whoisClass.php")
^ // <= right there
replace with:
require("whoisClass.php");
and it will run.
Having error reporting on, would have signaled the following error:
Parse error: syntax error, unexpected '$whois' (T_VARIABLE) in /user/home/whois.php on line 3
Always use error reporting:
error_reporting(E_ALL);
ini_set('display_errors', 1);
Footnotes:
When an error is reported on a certain line number, many times the error is on the line before that. In this case it signals being on line 3, yet it's actually on line 2.