you can do one thing...
using php and fsockopen
POST all the required form elements on the action page of the login form of phpmyadmin
check all the cookies that are recieved from the header, and set those cookies on the browser by setcookie
and now redirect the page to phpmyadmin index page, and you shall see yourself logged in
It is however tricky but extremely interesting...
It will help you understand how HTTP works !!!