daymobrew

I can probably manage to create a github account and add an issue, but a pull request would be beyond me as I have never used git (I use subversion locally).

@angelp357: Contact me via http://www.damiencarbery.com/contact/

A “site plugin” is not a plugin is unlikely to be useful to others as it would generally contain snippets of code for use on a specific site.

Putting my free shipping code into a plugin would definitely not be useful to others as the values are specific to my client’s site.

Just put it in your theme’s functions.php. That is an appropriate location.

Sorry for the confusion. I should not have mentioned “site plugin”

Perfect, thanks.
Here is my working code:

// Check shipping country for free shipping - 60 for Ireland (zone 1) and 100 for UK/Europe (zone 2).
add_filter('eshop_is_shipfree', free_shipping_checks, 10, 2);

function free_shipping_checks($shipfree,$total) {
  global $wpdb;

  $country_code=$_POST['ship_country'];
  $country_table=$wpdb->prefix.'eshop_countries';
  $ship_zone = $wpdb->get_var("SELECT zone FROM $country_table WHERE code='$country_code' limit 1");

  // Ireland is zone 1.
  if (($ship_zone == 1) && ($total >= 60)) {
    return true;
  }
  // UK/Europe is zone 2.
  if (($ship_zone == 2) && ($total >= 100)) {
    return true;
  }

  return $shipfree;
}

I don’t have a preference.
My first thought was a filter where the function’s return value is modified.
http://pastebin.com/P95V3sRh
The only variable I could think of passing was $total. Adding more will only lead to others requesting additional parameters.

An action would be pretty much the same.