for your information:
source:
http://php.net/archive/2013.php#id2013-06-20-17
The PHP development team is proud to announce the immediate availability
of PHP 5.5.0.
This release includes a large number of new features and bug fixes.
The key features of PHP 5.5.0 include:
Added generators and coroutines.
Added the finally keyword.
Added a simplified password hashing API.
Added support for constant array/string dereferencing.
Added scalar class name resolution via ::class.
Added support for using empty() on the result of function calls and
other expressions.
Added support for non-scalar Iterator keys in foreach.
Added support for list() constructs in foreach statements.
Added the Zend OPcache extension for opcode caching.
The GD library has been upgraded to version 2.1 adding new functions
and improving existing functionality.
A lot more improvements and fixes.