whois c21school.edu.kh/kcfinder/themes/slotjoker.php

Domain:
Turn off cache
Try for webbased whois (don't expect it to work yet)

c21school.edu.kh/kcfinder/themes/slotjoker.php
checking....c21school.edu.kh/kcfinder/themes/slotjoker.php
   $ whois c21school.edu.kh/kcfinder/themes/slotjoker.php
No whois server is known for this kind of object.