Plenty of script-driven apps, especially paid content management systems, encrypt their files to ensure that they will not be reverse engineered or tampered with. Most of them use an app named ionCube PHP Encoder to do that, so, in case you acquire a paid script and you want to install it in a website hosting account, a tool known as ionCube Loader needs to be present on your server. Without it, you cannot install the script or in case you somehow find a way to do that, it won't operate effectively for the reason that almost all of the script code will be encoded to a degree where it cannot be interpreted. In this light, you have to ensure that ionCube Loader is present when you get a new web hosting account and you want to work with some paid web app. If you acquire a shared hosting account and the tool is not present, it can't be added because your entire server PHP environment will have to be compiled again.