Page has Expired, BACK-button -problem in php

I have 2 pages where i have submit button on 1st page & on 2nd page i have previous button. Both the time i post the data means submit the forms two times. But when i clicked 2nd page's browser back button i get 1 st page with the data but if i click on 1st page's browser back button i get the Warning: Page has Expired. Can any one tell me the solution for? Also i have tried the

header("Expires: Sat, 01 Jan 2000 00:00:00 GMT");
header("Last-Modified: ".gmdate("D, d M Y H:i:s")." GMT");
header("Cache-Control: post-check=0, pre-check=0",false);
session_cache_limiter("must-revalidate");

this code for both the pages & my session is start on in the class file which i have included in the header of the page.

re: Page has Expired, BACK-button -problem in php

Heya, bharu.

You might find this article to be useful: http://www.mnot.net/cache_docs/.