The password features in PHP aren't exactly new, but I see lots of applications from "before" which aren't being migrated to better practices. I have some strategies for doing these migrations so I thought I'd share my main approach, plus a similar-but-different one I saw in the wild (OK it was in CakePHP, so not too wild!).
The examples here assume that you currently have either unsalted or all-with-the-same-salt passwords stored in your database, hashed with md5 or sha1 or something. This is a Very Bad Idea (TM) since it's trivial to recover unsalted passwords and not all that hard to figure out same-salted ones.
password_verify() functions which were included by
default in PHP 5.5 but are also available for PHP 5.3.9+ via a
userland implementation (see https://github.com/ircmaxell/password_compat). …