The state of play on your production server
The last few years we've had some pretty huge changes in LAMP land. PHP has gone up to version 5.4 now, which is vastly different (better) than 5.0; we have namespaces, array derefencing, new array notations, etc.
At the same time I feel there is a trend of people moving away from the tried and tested Apache to it's newer and leaner competitors like NGiNX and Lighttpd.
Meanwhile Oracle is closing off tests from the MySQL source and refusing to say why which makes its future uncertain. Will it stay open source and free, or will Oracle close it off bit by bit until it's completely closed? And if they do, will they keep it alive or kill it in the hope people will go and use their DBMS? There are a few alternatives like MariaDB and Postgres, while at the same time the traditional DBMSs are challenged by NoSQL solutions like MongoDB, CouchDB, etc.
Of course Linux is still Linux, and will always remain so. Versions have come and gone, but in terms of server usage not a whole lot has changed here.
All in all, it's not all that obvious anymore that anyone who runs PHP does this using a LAMP stack. Most will probably still be running LAMP, but there are a lot of other permutations that are getting more and more commonplace.
At work we're running CentOS Linux, because that's the distro we like best and the whole chkconfig system makes it very easy to setup and manage deamons. For the HTTP layer we've ditched Apache completely and are now running everything on NGiNX (and this coming from the Apache guru of the year 2011, I do see the irony in that) because it's a lot easier to configure (i.e. config files are much more readable) and we've found it performs a lot better than Apache. One thing I also particularly like about NGiNX is that more advanced stuff is disabled/not built in by default so you have to actively enable it, while Apache comes with a lot of bloat enabled by default you never ever use and just sits there hogging CPU and RAM for nothing, and you can then find out for yourself what is safe to disable and what isn't.
For the database we use PostgreSQL, because we have quite sensitive data and we rely on transactions a lot, and when it comes to transactions PostgreSQL is just better at that stuff (arguably, of course) than MySQL is. We're also running MongoDB, but that's for logging purposes only. It's just very handy to log a lot of contextual data with a log entry without knowing beforehand which fields you will be logging (and this also differs heavily per log item).
Lastly, we run PHP 5.3 via php-fpm. We are thinking of switching to PHP 5.4, but we need to test this extensively first before we feel comfortable rolling it out.
So, what about the rest of you guys? I'm curious to know what what you're running and why.