Codeigniter-sage-pay-direct is a project mainly written in PHP, it's free.
CodeIgniter Sage Pay DIRECT integration library
CodeIgniter Sage Pay Direct is a CodeIgniter library which makes it easy to use the DIRECT protocol, also, implements 3D secure payments.
Along with the library is a demo controller with two methods
If you take a look at the controller you will see how easy is to use this library.
You will need at least a SIMULATOR account in order to play with this library. You can apply for a SIMULATOR account here, it is free.
To report any issues visit this page