Checking if Billing and Shipping address are the same
I need to check that an orders billing and shipping addresses are the same so that we can avoid accepting orders in certain circumstances if they differ.
This needs to be done prior to, or when checking valid shipping methods for the delivery address. Or course this may not be fool proof as even if the "same" address is entered twice it may not be identical! Probably only the country and post code values would be relativly fool proof and sufficient to check.
I've tried and failed using Rules as they seem to want to check an entity value against a constant rather then another entity value. Can this be done with Rules or will I have to write a module with a hook-?? method. If a module what hook method would be the best to use?