Convert from Hash to Rails query

to_query.rb

require 'cgi'

def to_query(param, namespace = nil)
  case param
  when Hash
    param.collect do |key, value|
    unless (value.is_a?(Hash) || value.is_a?(Array)) && value.empty?
      to_query(value, namespace ? "#{namespace}[#{key}]" : key)
    end
    end.compact.sort! * '&'
  when Array
    prefix = "#{namespace}[]"
    if param.empty?
      to_query(nil, prefix)
    else
      param.collect { |value| to_query(value, prefix) }.join '&'
    end
  else
    "#{CGI.escape(namespace.to_s)}=#{CGI.escape(param.to_s)}"
  end
end