465115 Username Available - PHP/jQuery

I have a small job for someone with experience with php, jquery, and codeigniter framework. I already have the code written and working with my database, but I cant get it to work with the sign up form on my site. Go here to see it working. - [login to view URL] Use these username examples freelancer demolancer and what ever else for testing This should be quick and simple. I'll send the link of the page I want to incorporate it in to, to the winner.