Quoting Rene Pijlman, from the post of Sun, 08 Aug:
What's the best way to proceed? Install PHP 4.3 from source on woody? Or upgrade the machine to Debian sarge?
Do NOT upgrade a production server to testing! It has no security updates!
Ack.
well, actually 5 minutes after I posted this I saw a post from the Release Tzar. apperently Sarge is less than two months away from release, so starting August 12 it WILL be included in the security release system. still I'd wait another week or two to see that everything flows flawlessly.