Please read it

The game posts score to hscore.php in score variable. So - you will take it at hscore.php as $HTTP_POST_VARS["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