Changelog here: <a href="https://github.com/php/php-src/blob/php-5.5.0/NEWS" rel="nofollow">https://github.com/php/php-src/blob/php-5.5.0/NEWS</a><p>Highlights:<p>* Opcode cache (<a href="https://wiki.php.net/rfc/optimizerplus" rel="nofollow">https://wiki.php.net/rfc/optimizerplus</a>)<p>* Generators and coroutines (<a href="https://wiki.php.net/rfc/generators" rel="nofollow">https://wiki.php.net/rfc/generators</a>)<p>* "finally" keyword<p>* Constant array/string dereferencing<p>* Optimized access to temporary and compiled VM variables. 8% less memory reads.<p>* Dropped Windows XP and 2003 support.
Ww also have a modern framework for php. Everyone should try <a href="http://laravel.com/" rel="nofollow">http://laravel.com/</a> , such a fresh air into php development.
If you need a control panel for the nifty new Zend Opcache in PHP 5.5, please steal my ugly hack and improve it: <a href="https://gist.github.com/ck-on/4959032" rel="nofollow">https://gist.github.com/ck-on/4959032</a>