In our actual development, we may need to set the expiration time for the webpage to expire within a period of time. For example, if we use Chinacache CDN, how should we design it so that it can cache my content. in our actual development, we may need to set the expiration time for the webpage to expire within a period of time. For example, if we use Chinacache CDN, how should we design it so that it can cache my content.
In this way, no-cache is not used. this will convert no-cache to If-Modified-Since. therefore, we can write a program to control If-Modified-Since. note: in the cache system architecture, it is best to control the backend, so the best way is to manage the expiration by program.
The following is the program code:
Set the page to expire in 5 minutes.
$ Headers = apache_request_headers ();
$ Client_time = (isset ($ headers ['if-Modified-Since '])? Strtotime ($ headers ['if-Modified-Since ']): 0 );
$ Now = gmmktime ();
$ Now_list = gmmktime ()-60*5;
If ($ client_time <$ now and $ client_time> $ now_list ){
Header ('last-Modified: '. gmdate ('d, d m y h: I: S', $ client_time). 'gmt', true, 304 );
Exit (0 );
} Else {
Header ('last-Modified: '. gmdate ('d, d m y h: I: S', $ now). 'gmt', true, 200 );
}
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