Sometimes we need to control the expiration time of web pages such as home pages. But for example, if we use Chinacache’s CDN, how should we design it so that it can cache my content?
Of course, the prerequisite is to turn on a function reload_into_ims on in the CDN. In this way, users will not be afraid of sending no-cache. Because this will Convert no-cache to If-Modified-Since. So we write programs mainly to control If-Modified-Since. Remember, in the cache system architecture, it is best to be controlled by the backend, so it is best The only way is to use a program to manage expiration. Oh, I only know PHP, so I will write one in PHP. The same goes for other programs.
See my program below, haha, it expires in 5 minutes.
CODE:
<?php
$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 MYH:i:s', $client_time).' GMT', true, 304);
exit(0);
}else{
header('Last-Modified: '.gmdate('D, d MYH:i:s', $now).' GMT', true, 200);
}
?>