It's been a few years since PHP 5.3.0 was released (2009.06.30 if it matters to you), but now we have 5.4.0!
Here's a good shake down if you were holding out and ignoring spoilers the last few years.
Some of the key new features include traits, a shortened array syntax, a built-in webserver for testing purposes, use of $this in closures, class member access on instantiation, <?= is always available, and more!
PHP 5.4.0 significantly improves performance, memory footprint and fixes over 100 bugs. Notable deprecated/removed features include register_globals, magic_quotes (about time) and safe_mode. Also worth mentioning is the fact that multibyte support is enabled by default and default_charset has been changed from ISO-8859-1 to UTF-8.