If you want to use clickheat, but don't want to bother with mixing PHP and Ruby, or getting mixed-content warnings on SSL, etc.

gistfile1.rb

get '/c' => proc { |env|
    request = Rack::Request.new(env)
    params = request.params
    unless params['x'] && params['y'] && params['w'] && params['g'] && params['s'] && params['b'] && params['c']
      [200, {}, 'KO'] 
    else
      final = [params['s'].gsub(/[^a-z_0-9\-]+/, '_'), params['g'].gsub(/[^a-z_0-9\-]+/, '_')].join(',')
      log_path = Rails.root.join('log', 'clickheat', final)
      FileUtils.mkdir_p(log_path)
      File.open([log_path, "#{Time.now.strftime('%Y-%m-%d')}.log"].join('/'), 'a') do |f|
        f.puts [params['x'].to_i, params['y'].to_i, params['w'].to_i, params['b'].downcase.gsub(/[^a-z]+/, ''), params['c'].to_i].join('|')
      end
      [200, {}, 'OK']
    end
  }