I searched as well but didn't find anything conclusive. I did see that the last mention of DST was with version 5.0 of PHP but I'm using 5.2.
I saw references to varied versions of 5 (5.0 - 5.1.5), and
many people stating that things were normal with 4.x ... and
reports that it was working 5.1.6.
Maybe a bug was re-introduced in the 5.2 you're using?
Did you see a specific mention of this being a PHP failure?
Well ... if the OS reports the correct time, and the RDBMS
reports the correct time; but the PHP code doesn't. PHP
looks like a quite probable candidate. Did you restart
your machine after patching the time-zone file? Or at least
made sure that all services got restarted? Theoretically
it could still be apache, but you should see that in apache's
log; and you can test PHP from the command-line just for
$ date;php -r "echo strftime('%Y-%m-%d %H:%M:%S %Z%n');";php --version