PHP_CHILD

I wanted to create a simpe secured login form. after hours of googling i found tat using these will help 1.PDO statements. 2.session_hijackin soultions 3.password protection with salt My questions... 1.what else more should i add?? 2.i want to know if i want to use ajax here, will that make my site less-secured? if so, how do i use send data to check to db via ajax in a secured way?? Help plssss........... huge, loads of thanks in advances...