Validate flat shipping by weight

Hi

I understand some php, would like to put in flat shipping a weight limit (0,5Kg for my country), basically put a "if" for weight less 0,5Kg.

I do not know how to import the variable "$weight" and where would be the comparison, flat.php?


Thanks in advance

Why not just use the built-in Weight Based Shipping extension? You'd just enter a rate like this:

0.5:7.00

which would be a 7.00 cost for under 0.5 kg.