I wrote the following question:

How can I safely allow a php based website to create a linux user and interact with the environment?

I realize now that, based on a lack of understanding at the time, my question title is not exactly what I mean to ask.

What I mean to ask is "How can I automate the Linux account creation process after a new user signs up?" (Or, something similar.) My goal is to have an answer that explains how to do this, whether PHP is the correct approach or not.

There is some interest in the question. If I change the title, it alters it pretty substantially.

If the answer to that exact question is "You can't" (for sake of argument), well, technically that is an acceptable answer but I get no closer to solving my problem or having an answer for what I'm trying to accomplish, so would I accept it and write a new question that going to be extremely similar? Or should I alter the title of this one?