The error implies that mysqli is not available on the server.
Uncaught Error: Class 'mysqli_connect'
Can you create a page on your server with this code on it:
Then send me a link to that page and I'll take a look.
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.