Lots of script-driven applications, particularly paid content management systems, encode their files so as to make sure that they will not be reverse engineered or tampered with. Most of them use an app known as ionCube PHP Encoder to do that, so when you buy a paid script and you'd like to install it in a web hosting account, a tool known as ionCube Loader must be present on the server. Without it, you can't install the script or in case you somehow manage to do this, it will not function effectively as most of the script code will be encrypted to a degree where it can't be interpreted. In this light, you need to ensure that ionCube Loader is present when you get a fresh web hosting account and you would like to use some paid web app. If you acquire a shared hosting account and the tool is not present, it cannot be added as the entire server PHP environment will have to be compiled again.