PHP 5.4.16 and PHP 5.3.26 have been just released (see here)

If you use 64-bit WampServer and need a 64-bit Windows version of PHP 5.4.16, you can download it from here.

I am using always the latest version of PHP 5.4.x for all testing/development to make sure that there are no obvious PHP-related bugs, as the PHP5.4.x is much less forgiving and shows more bugs than PHP 5.3.x would.

So if you're a developer, I highly recommend to use PHP 5.4.x for all your testing.

Note: Do NOT use any PHP 5.3.x or PHP 5.4.x specific features as our minimum supported PHP version for XOOPS 2.5.x is still PHP 5.2.x. For XOOPS 2.6.0 the minimum supported version will be PHP 5.3