304: Not modified and front end caching

Question

I am using a PHP script to serve files. I would like to be able to send back a 304 not modified header in my http response if the file has not changed since th

Answer 1

There are also some others parameters to check .. in my case I didn't had both of those headers :

$_SERVER['HTTP_IF_NONE_MATCH'] && $_SERVER['HTTP_IF_MODIFIED_SINCE']

which are required to return a proper 304 header, as my system clock was a little late, It'll interpret those pages as expiring in the future, then not sending those values at all

Also check that header which is returned by apache, or at least override it to a bigger value

Cache-Control: max-age=3600

As it won't send previous headers if

Last-Modified previous sent header < ( NOW - 3600 )

So in my case I've set this pretty handy function function lastModified($file){ $x=filemtime($file); while($x>time())$x-=86000;}#reduce by one day if touched in future date $date=gmdate('D, j M Y H:i:s',$x).' GMT'; header('Cache-Control: max-age=86000',1); if($_SERVER['HTTP_IF_NONE_MATCH'] == $x || $_SERVER['HTTP_IF_MODIFIED_SINCE']==$date){ header('HTTP/1.1 304 Not Modified',1,304);die;} header('Etag: '.$x,1);header('Last-Modified: '.$date,1); }