ruby on rails - dealing with phpsessid using mechanize -

am trying crawl website everytime need phpsessid request_headers cookie firebug or return 500 , tried generate phpsessid using securerandom.hex(13) won't works , solution fix ?

   = mechanize.new     a.request_headers = {           "accept" => "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",           "content-type" => "application/x-www-form-urlencoded; charset=utf-8",           "host" => "www.website.com",           "referer" => "http://www.website.com/equipment",           "accept-encoding" => "gzip, deflate",           "x-requested-with" => "xmlhttprequest",           "pragma" => "no-cache",           "cookie" => "__alti_visits=1; __papvisitorid=#{securerandom.hex(16)}; __alti_visits=2; phpsessid=#{securerandom.hex(13)}; skimiuml=2; __altima_newvisit_detect=1;"             }       a.post("http://www.website.com/action",                   {                    "display" => "desktop",                    "category" => "#{product_type_id[c]}",                    "target" => "#{product_genre_id[a1]}"                   }) 

a similar question maintaining cookies between mechanize requests. did try that?