CPG-Nuke source documentation ⇒ CPG Dragonfly™ CMS
Files - Classes
  admin.php
includes
properties
functions
op

The option to set which "module" to show.
Without the op parameter your administration module isn't accesible.

HINT As of 9.0 this can be the first part of a file or module so you don't have to create a case.***.php file
For example admin.php?op=smilies opens admin/modules/smilies.php OR admin.php?op=News opens modules/News/admin/index.inc