The simplest and probably the best way performance-wise would be:
switch ($var2) {
case 1:
case 2:
$var3 = 'Weekly';
break;
case 3:
$var3 = 'Monthly';
break;
case 4:
case 5:
$var3 = 'Quarterly';
break;
}
Also, possible for more complex situations:
switch ($var2) {
case ($var2 == 1 || $var2 == 2):
$var3 = 'Weekly';
break;
case 3:
$var3 = 'Monthly';
break;
case ($var2 == 4 || $var2 == 5):
$var3 = 'Quarterly';
break;
}
In this scenario, $var2 must be set and can not be null or 0