During spring, there was a major change in php's way to handle variables received from flash or html forms. This change was made to address some security concerns
Before that time, variables from the form where simply available as php variables. The new php versions (4.1 or later) usually require you to pick up the vars from the form.
Now, there are many scripts around that have not been adapted to the new servers. On the other side, there are also quite a few hosting companies still running php versions from two years ago.
If your scripts fail to receive variables from your movies, please check
a) what is the php version on the server: simply upload a file phpinfo.php with that one line
<?php phpinfo(); ?>
in it and open it in the browser. The output will reveal the php version. If the version is 4.1 or later OR if the register_globals is off (somewhere down the page), then check
b) is the script suitable for new servers. If it was last modified before spring, probably not
Otherwise check whether at least one of $HTTP_GET_VARS, $HTTP_POST_VARS,
$_GET, $_POST or $_REQUEST occurs anywhere in your script. If not, your script has to be fixed.
Note: if you are testing on your own server, you can change the register_globals just to get the script working. This is not recommended: since it is a security thing, your hosting company will set it differently so your script fails if you upload to the web.