Lots of script-driven applications, particularly paid content management systems, encrypt their files in order to make sure that they will not be reverse engineered or tampered with. Many of them use an application called ionCube PHP Encoder to do this, so when you obtain a paid script and you intend to set it up in a web hosting account, a tool known as ionCube Loader has to be present on your server. Without it, you cannot install the script or if you somehow manage to do that, it will not function appropriately since almost all of the script code will be encoded to a point where it cannot be interpreted. In this light, you have to ensure that ionCube Loader is set up if you get a new web hosting account and you would like to take advantage of some paid web app. If you obtain a shared web hosting account and the tool is not present, it can't be added as the entire server PHP environment will have to be compiled again.