How do you load a PHP Variable from the page your movie is on?

I have a question about PHP variable… say I am loading my flash movie on a php page that has a variable called “myId” in the url of the page (http://www.mysite.com/mypage.php?myId=123).

How can I load that variable (myId) into my flash movie, send it to a php page (http://www.mysite.com/dynamicpage.php?myId=123), and then take the response and populate my movie?

Actually, I just need to know how to send it to a php page. I got the rest I think. Thanks!