A lot of script-driven apps, particularly paid cms, encrypt their files so as to make sure that they won't be reverse engineered or tampered with. Many of them use an application named ionCube PHP Encoder to do this, so, in case you buy a paid script and you would like to set it up in a hosting account, a software instrument known as ionCube Loader needs to be present on your server. Without having it, you cannot install the script or if you somehow manage to do that, it won't operate effectively for the reason that most of the script code will be encoded to a degree where it cannot be interpreted. In this light, you have to make sure that ionCube Loader is present when you get a fresh website hosting account and you would like to employ some paid web application. If you purchase a shared website hosting account and the tool is not present, it cannot be added since the whole server PHP environment shall have to be compiled again.