问题
In PHP, by default no cache related headers are sent.
HTTP/1.1 200 OK
Date: Fri, 19 Nov 2010 11:02:16 GMT
Server: Apache/2.2.15 (Win32) PHP/5.2.9-2
X-Powered-By: PHP/5.2.9-2
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 26
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Content-Type: text/html
Now, since by default it does not say anything about caching, can it result in say example.com/index.php getting cached in some situations?
回答1:
Yes. In general, every successful response may be cached unless there are some constrains:
Unless specifically constrained by a cache-control (section 14.9) directive, a caching system MAY always store a successful response (see section 13.8) as a cache entry, MAY return it without validation if it is fresh, and MAY return it after successful validation.
回答2:
Yes, usually the browser will cache certain files by default (usually images and css) if no rules have been setup on the server-side (see browser cache).
You can set up cache-control headers to control this, or disable it completely using:
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache");
See example #2 in header and read the note below it.
回答3:
can it result in say example.com/index.php getting cached in some situations?
It shouldn't, however there's a lot of implementations out there (particularly on mobile devices / mobile proxies) which don't behave correctly in this regard.
There's also also a lot of bad information about caching - the 'Pragma: no-cache' is meaningless when sent from a server.
To prevent caching:
header("Cache-Control: no-store, no-cache, must-revalidate");
When all else fails - check the manual
来源：https://stackoverflow.com/questions/4224485/caching-headers-from-php