i have upload the test file to the server and test it, it has no problem it's show null first and when click the first link it's turn to test and click second link stay the same
here is my checkout page i have attach it below
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.