register_globals off issues

I'm very new to PHP/mySQL and am working through the "PHP and mySQL for 
Dummies" examples. Unfortunately, these were all written with 
register_globals on and the system I'm using has register_globals off.

I'm having trouble converting the examples to use the $_POST() expression.

Specifically, the examples use a POST with a form variable to run a 
query and then unset this variable as such:

if (@$form == "yes")
{
unset($form);
}

I'm trying to convert this to use $_POST() as such:

  if (@$_POST['form'] == "yes")
{
unset($_POST['form']);
}

However, this does not work. It appears that you can't unset the 
$_POST['form'] array element.

Does anyone have any suggestions on how to fix this?
I know I'm probably missing a few very obvious things here... but I am a 
newbie.

/Mark
-- 
Mark H. Spohr
email: [email protected]