How does php static file return 304? Prompt Page not updated

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 } } Copy Code Description: This function can be called before a static file (slice) is output.

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