Login class checks if AJAX_PAGE is set to true and then does not print
the login html to the screen directly, but returns it in the _POST array
login_html, _POST action is set to login
It also resets _POST & _GET arrays before hand to avoid any misuese.
All _SESSION array access needs to be checked in any following class as
the _SESSION is unset in this moment
html element should be overwritten with this JS:
document.getElementsByTagName('html')[0].innerHTML =
data.content.login_html;