<% params.except(*@params_to_ignore+[fieldname[0], fieldname[1]]).each do |param, existing_val| %>
  <% val_arr = existing_val.is_a?(Array) ? existing_val : [existing_val] %>
  <% val_arr.each do |val| %>
    <%= hidden_field_tag(param, val, multiple: true) %>
    <% end %>
<% end %>
