To create FormEnum the first file that has to be modified is the UsesController.php :
After that user add.ctp file was altered:
Unfortunately refreshing the user add page returns error:
In order to fix this error FormEnumHelper.php helper has to be added to app/View/Helper.
Once this file has been added to the appropriate folder on the server admin can see drop-down menu for user roles:
To display drop-down disabled list for non-admin users, the following else statement was added to the already existing if statement (in add.ctp and edit.ctp files):
Right now new users can see disabled role during registration process:
And an existing non-admin users can also see disabled role on edit user profile page: