Sorry for the delay, but I had to come back from winter sports to have a decent Internet connection…
After being published by the PHP Group, PHP 5.2.9 anf its corresponding PECL extensions is now packaged for Lenny/Etch, amd64/i386. It fixes some annoying crashes and one security issue. The next release should be PHP 5.3.0 with some new interesting features (MySQL native driver, Phar, namespaces…).
Take a look at the official Changelog for more details before doing this recommanded upgrade.