PHP back page expired or no problem/click Refresh

Recently used PHP to do projects with a post to submit data and there is a session to do the record, run up, but there is a small problem, is submitted after the previous page will be back when it would appear page expired, to click Refresh can open this page, You can add a single statement to the PHP page to resolve

Header ("Cache-control:private");

· PHP back page expired or no problem

Cache-control "to control, the common value has private, No-cache, Max-age, must-revalidate, etc., the default for private. Its role is divided into the following situations according to different ways of re browsing:
1> Open a new window if the specified Cache-control value is private, No-cache, Must-revalidate, the server will be accessed again when a new window is opened. If the Max-age value is specified, then the server is not returned in the time within this value, for example: cache-control:max-age=5 means that access to the Web page after 5 seconds will not go to the server

2> in Address bar carriage return if the value is private or must-revalidate (unlike what is said on the web), the server is accessed only on the first visit and is no longer accessible. If the value is No-cache, it is accessed every time. If the value is Max-age, the access is not repeated until it expires.

3> Press the Back button if the value is private, must-revalidate, Max-age, it will not be accessed, and if it is No-cache, repeat access each time

4> Press the Refresh button regardless of the value, it will be repeatedly accessed when the specified Cache-control value is "No-cache", accessing this page does not leave a page backup on the Internet temporary article folder.