thanks for the advice about the weight units (pounds, grams, etc) and the = sign!

i think i'm almost there with the flat rate weight ranges (0-250g = $10, etc) but i have another coding question:

for a few reasons, i'd like the variables for minimum weight, maximum weight and maximum amount to be optional. i've set them so that NULL = yes and DEFAULT = null in the database table, but blank fields are still being set to "0" instead of remaining empty. i suspect this is something in the php? these variables are all "float" and "unsigned". i tried removing floatval, but to no avail. none of them are passing through the validation script, so it can't be that...