Question

We were wondering,

Header wise… What does a proper etag response look like.

Etag response, in the sense that an e-tagged request is made, and yes it matches the etag on our end, thus no content must be sent.

Does it need to contain a content-length header?

Do we use a 304 header response?

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Claritifaction:

We want to etag handle via php.

The flow is as follows:

a) Etagged request comes in.

b) PHP checks the etag to see if it meets what we think is a proper condition NOT to send back a full document body.

c) What do we manually send back via php to signal to the browser to use the cached content?

Thanks!

Answer 1

Answered my own question after reading the wiki as lanzz sudgested in the comment above:

“In this subsequent request, the server may now compare the client’s
ETag with the ETag for the current version of the resource. If the
ETag values match, meaning that the resource has not changed, then the
server may send back a very short response with an HTTP 304 Not
Modified status. The 304 status tells the client that its cached
version is still good and that it should use that.”

So yes, a 304 response is the correct way to answer an etagged request if you want the user agent to use the cached copy.