We don't tend to use PHP very much, but it seems to be fairly popular. Here are some links we find helpful:
An example of PHP outputting RSS
A very nice RSS1.0 writer class is also on the web
Migration tool for PHP: ladder. Does its thing without any extra dependancies.
PHP version of OmniAuth: HybridAuth
PHP and password security
PHPpass: This is a portable public domain password hashing framework for use in PHP applications, which tries various ways of encrypting the password, until it finds one that the running version of PHP supports (Tutorial
Password code from DokuWiki, standalone
Simple PHP auth system. If I were building my own auth system I'd start here, add strong encryption.