On his Gentoo blog, Stuart Herbert has posted this update about the dev-lang/php packages being stabillised for the distribution of the OS.
We're stabilising PHP-4.3.11 (for the folks who haven't ported packages to work with PHP 4.4's reference changes), PHP 4.4.1, and PHP 5.0.5 (for the early adopters who have binary-encrypted packages). PHP 4.4.2 and PHP 5.1.2 will be stabilised sometime in March (is my best guess).
On Wednesday, Luca filed a request to stabilise our new dev-lang/php packages. As of this morning, these are now the standard packages on the PPC64 and x86 architectures.
He also lists some of the advantages that these new packages will bring to Gentoo, like: PHP5 support, a "one package install", the ability to run PHP4 and PHP5 concurrently, and the ability to install PECL packages easily.