[Dovecot] Slightly off topic question but ...

[Marc Perkel]

I'm using files for passwords that look like the unix passwd and shadow 
files, except each domain has it's own pair of shadow and password files 
for that domain. And dovecot works fine with that.

So - here's my off topic question. I'm trying to create a PHP interface 
to allow user to change their password in these passwd / shadow file 
combos. What kind of encryption do they use and specifically what PHP 
command would I use to encrypt a password like the shadow file has?

Thanks in advance.