Dmitry posted results of performance test comparing PHP 5.2 and 5.3 to internals which are impressive numbers:
- Drupal 20% faster
- Qdig 2% faster
- typo3 30% faster
- wordpress 15% faster
- xoops 10% faster
Up to 30% performance win by simply updating PHP! Please help us with the quality assurance and test your applications using a 5.3 snapshot - we can't cover every usecase, you can!
And again as a sidenote: 5.2.6RC2 is out, please test that, too 
Tuesday, March 25. 2008 at 16:30 (Link) (Reply)
http://www.thinkingphp.org/2007/09/26/php-521-was-a-evil-release-check-your-server/
P.S. Is your layout intended to be this 'odd'?
Tuesday, March 25. 2008 at 22:54 (Reply)
well, we always try to improve our releases. For benchmarks: See also Sebastians results at
http://sebastian-bergmann.de/archives/745-Benchmark-of-PHP-Branches-3.0-through-5.3-CVS.html
And about the design here: Yeah, I should sit down and improve it, it's somewhere on my TODO.
Tuesday, March 25. 2008 at 17:42 (Reply)
SCNR
Tuesday, March 25. 2008 at 21:49 (Reply)
Wednesday, March 26. 2008 at 09:48 (Link) (Reply)
Tuesday, April 8. 2008 at 21:13 (Reply)
Wednesday, April 9. 2008 at 22:20 (Reply)
Thanks!
Monday, March 16. 2009 at 15:36 (Reply)
http://www.webdigi.co.uk/blog/2009/what-is-new-in-php-53-for-php-amateurs/
Friday, August 5. 2011 at 22:26 (Link) (Reply)
i'm now in a process of performance-optimization and i'm using 5.1.6 - i think i will try an upgrade.
best,
martin