gistfile1.txt

function filterProvinces(element, countryCode) {
    $(element).val(0);
    optGroups = $(element).data('options');
    $(optGroups).each(function(){
        var match = false
        if ($(this).data('country_code') == countryCode) {
            $(element).append($(this));
        }
    })
    $(element).find('optgroup').remove();
}


$(document).ready(function(){

    province = $("select[name=province]");
    opts = $(province).find('optgroup').each(function(){
        //zf2 doesnt allow non-standard option attributes.. hooray.
        $(this).attr('data-country_code', $(this).children().val().substring(0,2));
    });
    console.log(opts);
    $(province).data('options', $(opts));   //store as data val
    $(province).find('optgroup').remove();  //remove the elements

    $("select[name=country]").live('change', function() {
        province = $(this).siblings("select[name=province]");
        val      = $(this).val();
        filterProvinces(province, val)
    });
});