The game posts 4 variables to hscore.php:
Calc score as score=a+b-2*c
Calc framerate as framerate=a-c
You need d to validate input: d=7*framerate+3*score
How to store scores, show highscores table and track/register users - it's your business. Usually it makes with cookies - your user login, you give him session ID in cookies. When flash posts a score you check the session ID and process the score.
BR. Your Ghost