Plenty of script-driven applications, especially paid content management systems, encrypt their files so as to make sure that they will not be reverse engineered or tampered with. The majority of them use an application called ionCube PHP Encoder to do that, so if you buy a paid script and you wish to install it in a hosting account, a software instrument called ionCube Loader needs to be present on the server. Without it, you will not be able to install the script or if you somehow find a way to do this, it won't function appropriately since most of the script code will be encrypted to a point where it can't be interpreted. That's why, you need to ensure that ionCube Loader is set up when you get a new website hosting account and you wish to employ some paid web application. If you get a shared web hosting account and the tool is not present, it can't be added as your entire server PHP environment will have to be compiled again.