HTTP_POST_VARS['var'] displayed but not $var

Hi, I recently installed the php-4.2.2-Win32 cgi and have come across a problem. When I have form variables, I can only read them via $HTTP_POST_VARS['var'] and *not* simply via $var. i.e. echo $HTTP_POST_VARS['Qmin']; // works a charm echo "<br><br>$Qmin"; // doesn't work I've installed PHP many times and have never encountered this problem. I'm guessing (hoping) that this is controlled in php.ini or can be fixed, but a search for a solution has proved unsuccessful thus far. Does anyone know what the problem is? Cheers, Lee