PHP Header - 位置重定向似乎丢失了缓存

Question

I'm doing some cURL checks on response codes of files before redirecting requests to different hosts (to make sure the files exist before I redirect).

When we're all happy, I send them off-server to remote host and we're all happy.

The only problem seems to be it's not caching on the user's machine. Is there something I can do to let the user browser know this is the same file? I thought it would inherently know as it's just a header location redirect (ie header('location:http://www.locationtogo.com/asda?242');

Thanks for any help!

------- UPDATE ----------

Seems to be quite a few questions on this; so let me explain step by step...

1. User requests file from handler.php
2. handler.php does cURL check to see if response code is
3. if response code is 200 I was redirecting to the file
4. however each time reloaded the handler.php for the same file... it would reload the entire file

I've now realised - stupid mistake - but will list here just incase anyone experiences the same - I was of course, looking for response 200, not 200 or 304.

This is now caching.

Answer 1

You need to add a Cache-Control or Expires header along with the redirect to indicate that it can be cached.

Example (this will allow the browser to cache the response for an hour)

header('Cache-Control: max-age=3600')

Answer 2

PHP and apache will not cache a PHP file by default. I recently ran into this myself. You can however return a 304 if you want and that will fix the problem. I did it with etags.

Simply send the browser the first time an etag hash the first time it visits it.

header('Etag: '.$eTagHash);

Then, check to see if the etag is there, if so tell the browser it's a 304 not modified.

if(isset($_SERVER['HTTP_IF_NONE_MATCH'])) {
    if(trim($_SERVER['HTTP_IF_NONE_MATCH']) == trim($eTagHash)){
       header("HTTP/1.1 304 Not Modified");
       exit;
    }}

You can set the $eTagHash to anything you want. You should have etags enabled on the apache server as well (most do).

If you ever need to redirect somewhere else, just change the etag hash and when it doesnt match you can send the browser the header etag again with the new value.