#enviroment.rb
...
require 'to_xml_extensions'

#lib/to_xml_extensions.rb
module WillPaginateHelpers
  include ActiveSupport::CoreExtensions::Array::Conversions
  def to_xml_with_collection_type(options = {})
        serializeable_collection.to_xml_without_collection_type(options) do |xml|
          xml.tag!(:current_page, {:type => ActiveSupport::CoreExtensions::Hash::Conversions::XML_TYPE_NAMES[current_page.class.name]}, current_page)
          xml.tag!(:per_page, {:type => ActiveSupport::CoreExtensions::Hash::Conversions::XML_TYPE_NAMES[per_page.class.name]}, per_page)
          xml.tag!(:total_entries, {:type => ActiveSupport::CoreExtensions::Hash::Conversions::XML_TYPE_NAMES[total_entries.class.name]}, total_entries)
        end.sub(%{type="array"}, %{type="collection"})
      end
      alias_method_chain :to_xml, :collection_type
 
      def serializeable_collection #:nodoc:
        # Ugly hack because to_xml will not yield the XML Builder object when empty?
        empty? ? returning(self.clone) { |c| c.instance_eval {|i| def empty?; false; end } } : self
      end
end
 
WillPaginate::Collection.send(:include, WillPaginateHelpers)

<?xml version="1.0" encoding="UTF-8"?>
<time-cards type="collection">
  <current_page type="integer">1</current_page>
  <per_page type="integer">25</per_page>
  <total_entries type="integer">108</total_entries>
  <time_card>
    <approved type="boolean">false</approved>
    <billable type="boolean">false</billable>
    <created_at type="datetime">2008-10-10T14:04:13-04:00</created_at>
    <date type="datetime">2008-10-10T14:04:13-04:00</date>
    <has_been_billed type="boolean">false</has_been_billed>
    <has_been_paid type="boolean">true</has_been_paid>
    <hours type="float">2.0</hours>
    <id type="integer">98</id>
    <is_overtime type="boolean">false</is_overtime>
    <task_id type="integer">6</task_id>
    <updated_at type="datetime">2008-10-10T14:04:13-04:00</updated_at>
    <user_id type="integer">1</user_id>
  </time_card>
  ...
</timecards>

class ExportSearch
 
  def timecards
    find_cards
  end
 
  def users(u)
    @u = u
  end
 
  def projects(p)
    @p = p
  end
 
  def tasks(t)
    @t = t
  end
 
  def dates(date1, date2)
    @d1 = date1
    @d2 = date2
  end
 
  def clients(c)
    @c = c
  end
 
private
 
  def find_cards
    TimeCard.find(:all, :conditions => conditions, :include => {:task => :project}, :order => :date)
  end
 
  def projects_conditions
    ["tasks.project_id IN (?)", @p] unless @p.blank?
  end
 
  def client_conditions
    ["projects.client_id IN (?)", @c] unless @c.blank?
  end
 
  def date_conditions
    ["date BETWEEN ? AND ?", @d1, @d2] unless (@d1.blank? || @d2.blank?)
  end
 
  def task_conditions
    ["task_id IN (?)", @t] unless @t.blank?
  end
 
  def users_conditions
    ["user_id IN (?)", @u] unless @u.blank?
  end
 
  def conditions
    [conditions_clauses.join(' AND '), *conditions_options]
  end
 
  def conditions_clauses
    conditions_parts.map { |condition| condition.first }
  end
 
  def conditions_options
    conditions_parts.map { |condition| condition[1..-1] }.flatten
  end
 
  def conditions_parts
    private_methods(false).grep(/_conditions$/).map { |m| send(m) }.compact
  end
end

    search = ExportSearch.new
    search.users(params[:export][:users].join(',')) unless params[:export][:users].blank?
    search.tasks(params[:export][:tasks].join(',')) unless params[:export][:tasks].blank?
    search.projects(params[:export][:projects].join(',')) unless params[:export][:projects].blank?
    search.dates(start_date, end_date)
 
    @time_cards = search.timecards