When you post forms with php, or any other data, you may come back to the page and find a message in the browser like “Document Expired” or “Confirm Form Resubmission With Chrome”. These messages are a safety precaution the browser uses with sensitive data such as post variables. The browser will not automatically give you the fresh page again. You must reload the page by clicking try again or with a page refresh. Then, it operates as you would expect it to.
However, the php coder can work around the annoying message from the browser by adding a little code into the script. The example shows a couple of lines of code that can be added above session_start() in order to be able to go back and forth to the page when you post without any hangups.The ‘private_no_expire’ mode means that the client will not receive the expired header in the first place.
header('Cache-Control: no cache'); //no cache
session_cache_limiter('private_no_expire'); // works
//session_cache_limiter('public'); // works too
session_start();