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PHP cleverly uses 304 code to cache image files

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2016-07-25 08:52:151287browse
  2. private function _addEtag($file) {
  3. $last_modified_time = filemtime($file);
  4. $etag = md5_file($file);
  5. // always send headers
  6. header("Last-Modified: ".gmdate ("D, d M Y H:i:s", $last_modified_time)." GMT");
  7. header("Etag: $etag");
  8. // exit if not modified
  9. if (@strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE ']) == $last_modified_time ||
  10. @trim($_SERVER['HTTP_IF_NONE_MATCH']) == $etag) {
  11. header("HTTP/1.1 304 Not Modified");
  12. exit;
  13. }
  14. }
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Just call it before outputting static files (such as pictures).



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