...would like a set of variables...? From the dropdown menu, they select one of the numbers and submit to the next page. Then this page I have $var1 through $var20, and I want the values of $var1 through whatever number they pick to be 1, and the rest to be 0. Would it be as simple as:

for($start = 1, $start <= $numfields, $start++){
$var.$start = 1;
}