Shiney new PHP for 10.04.
Recently PHP was updated to use PHP 5.3.1 by default. The reason for this is that Lucid is a LTS and support for PHP 5.2 will eventually go away during the life time of Lucid on Ubuntu Server.
So please check your web applications, the transition has been a little bumpy for those users who are running Lucid right now, but most of those issues should be fixed now. Please report any bugs that you find on launchpad so we can keep track of them and fix them as soon as possible.
If you have any questions please let me know.