The latest version of the PHP language (in the PHP 5 series) has been released today - PHP 5.2.1:

The PHP development team would like to announce the immediate availability of PHP 5.2.1. This release is a major stability and security enhancement of the 5.X branch, and all users are strongly encouraged to upgrade to it as soon as possible. Further details about this release can be found in the release announcement 5.2.1, the full list of changes is available in the ChangeLog PHP 5.

Among the security enhancements and bug fixes in this new release are:

• Prevent search engines from indexing the phpinfo() page.
• Fixed possible overflows and stack corruptions in the session extension.
• Fixed possible clobbering of super-globals in several code paths.
• Fixed a possible buffer overflow inside mail() and ibase_{delete,add,modify}_user() functions.
• and much more...

Ilia Alshanetsky (release manager for the PHP 5 series) also has posted some comments about the release to his blog.