PHP has many versions like PHP 1, PHP 2, PHP 3, PHP 4 and PHP 5 among others. Every version of PHP comes with all new and exciting features. PHP does not have native support for Unicode or multi byte strings because it is under development for a future version of PHP. This Unicode support will allow strings as well as class and function names to contain non-ASCII characters. PHP 4 or PHP parser compiles input to produce byte code for processing by the Zend Engine, giving a whole new improved performance.