Lots of script-driven applications, especially paid cms, encode their files in order to ensure that they won't be reverse engineered or tampered with. Most of them use an application named ionCube PHP Encoder to do that, so if you obtain a paid script and you'd like to set it up in a hosting account, a software instrument known as ionCube Loader must be present on the server. Without having it, you can't install the script or in case you somehow find a way to do this, it won't work properly for the reason that almost all of the script code will be encrypted to a degree where it can't be interpreted. That is why, you need to ensure that ionCube Loader is present when you get a fresh hosting account and you'd like to take advantage of some paid web application. If you purchase a shared web hosting account and the instrument is not present, it cannot be added since the whole server PHP environment will have to be compiled again.