The PHP package was rebuilt in order to provide more functionality while reducing explicit dependencies and memory usage. This was achieved by building most PHP modules as shared objects instead of building them statically in.
In addition to this it is easier to use and package external PHP modules and its configuration due to the possibility to have a separate config file for every extension. Those ini files are stored in /etc/php/conf.d/ and will automatically used by PHP.
If you are using PHP on a webserver connected to the internet you might be interested in installing the php-suhosin package as well which was moved from the [community] into the [extra] repository. Along with the suhosin-patch which ships with the current PHP packge this extension provides some advanced security features. For some more information on this see http://www.suhosin.org.
The packages will remain in [testing] for at least a few days. Please test this package with your favorite scripts and report any error or suggestions: http://bugs.archlinux.org
If you update from a previous PHP setup, take care of the following changes:
Due to the modularization you have to enable some modules which were built-in before. For a quick overview compare the modules section at the bottom of your php.ini with the new one which will be stored as php.ini.pacnew
PHP itself does not have any explicit dependencies, but some extensions will only work with certain package installed. Those will be displayed during the installation.
If you are using any PHP extension from [community] or AUR you will have to rebuild them against this PHP version. As soon as this package arrives in [extra], all extensions in [community] will be updated.