[Dovecot] Slightly off topic question but ...

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.