404 Caching returns HTTP 200 status code for 404 pages

[raamdev]

When the 404 Caching option is enabled, Quick Cache caches the 404 page and serves the cached file upon all subsequent 404 errors. However, it also returns a 200 OK HTTP status code, instead of the proper 404 Not Found.

Here's how you can reproduce this:

1. Enable 404 Caching
2. Visit a non-existent page to create a 404 cache file
3. Run wget --server-response <non-existent page URL> and observe the output
4. Disable Quick Cache 404 Caching
5. Run wget --server-response <non-existent page URL> and observe the output

Note that with Quick Cache 404 Caching disabled, WordPress returns the correct HTTP status code.

# ----------- Quick Cache 404 Caching Enabled

$ wget -v http://qcpro.dev/asdasd
--2014-06-05 14:59:23--  http://qcpro.dev/asdasd
Resolving qcpro.dev (qcpro.dev)... 127.0.0.1
Connecting to qcpro.dev (qcpro.dev)|127.0.0.1|:80... connected.
HTTP request sent, awaiting response... 200 OK

# ----------- Quick Cache 404 Caching Disabled

$ wget -v http://qcpro.dev/asdasd
--2014-06-05 15:00:50--  http://qcpro.dev/asdasd
Resolving qcpro.dev (qcpro.dev)... 127.0.0.1
Connecting to qcpro.dev (qcpro.dev)|127.0.0.1|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2014-06-05 15:00:51 ERROR 404: Not Found.

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See http://wordpress.org/support/topic/cached-404-returns-200

[jaswrks]

Ah.. I see. Darn, this actually comes back to the issue with PHP itself, where headers_list() is currently missing the HTTP status code header. Quick Cache would pick this up properly if that were not broken.

From this line in the dev branch.

file_put_contents($cache_file_tmp, serialize(headers_list()).'<!--headers-->'.$cache)

What we could do is stuff the 404 header into the cache file like we already do for the other headers preserved by this line inside the advanced-cache.tpl.php file. In a case where there is a 404 detected, the 404 cache file can include the 404 response header and Quick Cache will repeat this automatically on each subsequent cache hit to that 404; whether it be through a symlink or not.

[jaswrks]

@raamdev I will have to work with this portion of the code when I work on #56, would you like me to fix this also at the same time?

[raamdev]

@jaswsinc Yes, if you could fix this along with #56, that would be great! I've assigned this to you. Thanks!

[raamdev]

Closed by #219.