referring_keywords.rb

# from http://www.insiderpages.com/rubyonrails/2007/01/get-referring-search-engine-keywords.html 

def setup_referring_keywords
  # Check whether referring URL was a search engine result
  referer = @request.env["HTTP_REFERER"]
  unless referer.nil_or_empty?
    search_referers = [
      [/^http:\/\/(www\.)?google.*/, 'q'],
      [/^http:\/\/search\.yahoo.*/, 'p'],
      [/^http:\/\/search\.msn.*/, 'q'],
      [/^http:\/\/search\.aol.*/, 'userQuery'],
      [/^http:\/\/(www\.)?altavista.*/, 'q'],
      [/^http:\/\/(www\.)?feedster.*/, 'q'],
      [/^http:\/\/search\.lycos.*/, 'query'],
      [/^http:\/\/(www\.)?alltheweb.*/, 'q']
    ]
    query_args =
      begin
        URI.split(referer)[7]
      rescue URI::InvalidURIError
        nil
      end
    search_referers.each do |reg, query_param_name|
      # Check if the referrer is a search engine we are targetting
      if (reg.match(referer))
        # Create a globally scoped variable (@referring_search) containing the referring Search Engine Query
        unless query_args.nil_or_empty?
          query_args.split("&").each do |arg|
            pieces = arg.split('=')
            if pieces.length == 2 && pieces.first == query_param_name
              @referring_search = CGI.unescape(pieces.last)
              return true
            end
          end
        end
        return true
      end
    end
  end
  true
end