Some of the useful fields that ph contains are:
For example, I read my mail on my home machine, dynamic.isdn.uiuc.edu. So I have my ph email field to "email@example.com". I advertise my email address as "firstname.lastname@example.org". When people mail me, it goes to the ph redirector, which sends it to my home machine.
This is extremely useful when you change locations. Say I decided to read my mail on the student cluster instead of on my home machine. All I would need to do is change my email field to "email@example.com", and everyone could continue mailing me at "firstname.lastname@example.org" just like they always have. They wouldn't even know the difference.
The URL for my homepage is currently http://www.cen.uiuc.edu/~roth. This is in my www field. People access my homepage as http://www.uiuc.edu/ph/www/roth. If I ever wanted to move my homepage to the student cluster, I could change my www field to http://www.students.uiuc.edu/~roth, and people could continue to use the same URL they'd been using.
First, run the ph client program by typing ph.
Second, log in to the ph server by typing login ph_alias (where ph_alias is your ph alias).
To edit any field, type edit field_name. ph will invoke your editor for you based on the EDITOR environment variable. You can type fields to get a comprehensive list of fields.
To exit ph, type bye.