Lots of licensed and some free script-driven applications have protected code, which isn't human readable. The idea behind this is to avoid the reverse engineering as well as the not authorized use of such apps. One of the most popular encryption tools used for this particular purpose is called Zend Guard and it is commonly used since it can be used to alter all PHP 4 or PHP 5 code. The only way for the encoded files to run the right way on a web server after that is when an additional tool called Zend Optimizer is available. In the event that you wish to work with any paid web software which needs Zend Optimizer, you should make sure that it's set up on the server where you'll host your site. Also, sites which need the instrument will perform better since their code is already precompiled and optimized, which means that it is executed quicker.