The launch of PHP v.4 marked a serious progress in the popularity and utilization of this programming language. PHP v. 4 is the first version powered by the Zend Engine, which allows working with encoded files through the Zend Optimizer. The Zend Engine-powered PHP v. 4 is more efficient, more reliable, and much, much faster than PHP v.3. This optimized performance results from the redesign of the scripting engine used in PHP v.4 - the engine has been entirely rewritten and uses a significantly more efficient "compile-then-execute" paradigm, instead of the "execute-while parsing" model employed in PHP 3.0.