login (php) with javascript

[Webby0815]

I am trying to add a login scroll-down window in my page. The window itself works fine (http://pasionesargentas.webatu.com/test4.php), but now I need some help- I need an approach as to how to integrate the new input form to my actual log in system. In the scroll-down window you see the two fields (username and password) and the submit button. But the actual login system I have a totally new window (http://pasionesargentas.webatu.com/signin.php) where I do the whole checking and session start. I could probably merge the php login code with the scroll-down window, but I would not prefer to do that since that scroll-down window is in the header and I wouldn't like to run the check every single time a page (with the header) is opened. I am really afraid of not being understood so here I am adding some more lines of the same:I have a javascript scroll down window with two fields (u/n and pass) and a submit button but I don't know how to check those values with the database so I can start the session for that user.