caching – Testing a 304 response code implementation in PHP-ThrowExceptions

Exception or error:

I have an API and I’ve been trying to add cache control headers to it.

The API already makes use of PhpFastCache for server side caching but I wanted to add an additional layer of browser control caching. I came across this intelligent php cache control page and modified it slightly.

Using PhpFastCache, I do a check to see if the server side cache exists, if it doesn’t then query the DB and output normally with a 200 response code. If the cache does exist then I do the following:

//get the last-modified-date of this very file
$lastModified=filemtime(__FILE__);
//get a unique hash of this file (etag)
$etagFile = md5( $CachedString->get() );
//get the HTTP_IF_MODIFIED_SINCE header if set
$ifModifiedSince=(isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) ? $_SERVER['HTTP_IF_MODIFIED_SINCE'] : false);
//get the HTTP_IF_NONE_MATCH header if set (etag: unique file hash)
$etagHeader=(isset($_SERVER['HTTP_IF_NONE_MATCH']) ? trim($_SERVER['HTTP_IF_NONE_MATCH']) : false);

//set last-modified header
header("Last-Modified: ".gmdate("D, d M Y H:i:s", $lastModified)." GMT");
//set etag-header
header("Etag: $etagFile");
//make sure caching is turned on
header('Cache-Control: public');

//check if page has changed. If not, send 304 and exit
if (@strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE'])==$lastModified || $etagHeader == $etagFile)
{
   header("HTTP/1.1 304 Not Modified");
   exit;
}else{
    //Cache Match - Output Cache Result
    header('Content-Type: application/json');
    echo $CachedString->get();        
}   

I’m using this line to get the cached response as md5:

$etagFile = md5( $CachedString->get() );

Then doing a check to see if this md5 content has changed:

if (@strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE'])==$lastModified || $etagHeader == $etagFile)
{
   header("HTTP/1.1 304 Not Modified");
   exit;
}else{
    //Cache Match - Output Cache Result
    header('Content-Type: application/json');
    echo $CachedString->get();        
} 

However I can never seem to get the 304 response header. It is ALWAYS a 200 code response header.

curl -I -L  https://db.ygoprodeck.com/api/v7/cardinfo.php?name=Tornado%20Dragon

With the response always being:

HTTP/1.1 200 OK
Date: Tue, 17 Mar 2020 13:37:31 GMT
Content-Type: application/json
Connection: keep-alive
Set-Cookie: __cfduid=daaab295934a2a8ef966c2c70fe0955b91584452250; expires=Thu, 16-Apr-20 13:37:30 GMT; path=/; domain=.ygoprodeck.com; HttpOnly; SameSite=Lax
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET
Access-Control-Allow-Headers: Content-Type, Authorization, X-Requested-With
Cache-Control: public
Last-Modified: Tue, 17 Mar 2020 13:15:53 GMT
Etag: 399b9ba2d69ab115f46faa44be04d0ca
Vary: User-Agent
CF-Cache-Status: DYNAMIC
Expect-CT: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
Server: cloudflare
CF-RAY: 57571be8a986a72f-DUB
How to solve:

Your request is being proxied through Cloudflare which has its own caching layer. If you test this direct to origin/with a grey clouded record are you getting a 304?

You said you were working on browser caching, browser is going to cache based on the max-age setting you send, but don’t see one being set in the response.

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