Php static file return 304 tip _ php instance

This article mainly shares a tips on returning 304 for php static files. If you need a friend, you can refer to the following: sometimes some static files (slices) will be output by php and you will find that all requests are 200, it is a waste of resources to request static files on the server every time. How can I cache images in the browser? We need to output 304 in php.

We can use HTTP_IF_MODIFIED_SINCE and etag in php to do this. Etag does not have a clearly defined format. We can use the md5 value of the file modification time. The Code is as follows:

The Code is as follows:

Private function _ addEtag ($ file ){
$ Last_modified_time = filemtime ($ file );
$ Etag = md5_file ($ file );
// Always send headers
Header ("Last-Modified:". gmdate ("D, d m y h: I: s", $ last_modified_time). "GMT ");
Header ("Etag: $ etag ");
// Exit if not modified
If (@ strtotime ($ _ SERVER ['HTTP _ IF_MODIFIED_SINCE ']) = $ last_modified_time |
@ Trim ($ _ SERVER ['HTTP _ IF_NONE_MATCH ']) = $ etag ){
Header ("HTTP/1.1 304 Not Modified ");
Exit;
}
}

In the code, you can call it before the static file (slice) is output.