Two methods to support page retreat using PHP programs_PHP Tutorial

First, use the Header method to set the message header Cache-control


QUOTE:
header('Cache-control: private, must-revalidate'); //Support page bounce

Second, use the session_cache_limiter method


QUOTE:
//Note to write before the session_start method
session_cache_limiter('private, must-revalidate');

Supplement:
Cache-Control message header field description
Cache-Control specifies the caching mechanism followed by requests and responses. Setting Cache-Control in a request message or response message does not modify the caching process during the processing of another message. The caching instructions during the request include no-cache, no-store, max-age, max-stale, min-fresh, only-if-cached, and the instructions in the response message include public, private, no-cache, no-store, no-transform, must-revalidate, proxy-revalidate, max-age. The meaning of the instructions in each message is as follows:

Public indicates that the response can be cached by any cache area.

Private indicates that all or part of the response message for a single user cannot be processed by the shared cache. This allows the server to only describe a partial response from a user that is not valid for other users' requests.

no-cache indicates that the request or response message cannot be cached

no-store is used to prevent important information from being released unintentionally. Sending it in the request message will cause both the request and response messages to use caching.

max-age indicates that the client can receive responses with a lifetime no greater than the specified time (in seconds).

min-fresh indicates that the client can receive responses with a response time less than the current time plus the specified time.

max-stale indicates that the client can receive response messages beyond the timeout period. If you specify a value for max-stale messages, the client can receive response messages that exceed the specified value of the timeout period.



About form refresh

Q: Why are all the field information cleared after I click the browser’s back button?

A: This is because you used the session_start function in your form submission page. This function will force the current page to not be cached. The solution is to add header("Cache-control: private") after your Session_start function; Note that your PHP program cannot have any output before this line.

Supplement: There is also a session-based solution, add


QUOTE:
session_cache_limiter('nocache');//Clear the form
session_cache_limiter ('private'); //Do not clear the form, only while the session is in effect
session_cache_limiter('public'); //Do not clear the form, just as if the session is not used

Can be used in session_start(); Add session_cache_limiter("private,max-age=10800");

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