ResponseTagger helps you keep track of tags for a response. It can add
the tags as a response header that you can later use to invalidate all cache
entries with that tag.
Make sure to configure your proxy for tagging first.
The response tagger uses an instance of
TagHeaderFormatter to know the
header name used to mark tags on the content and to format the tags into the
correct header value. This library ships with a
CommaSeparatedTagHeaderFormatter that formats an array of tags into a
comma-separated list. The format for specifying the tags depends on the caching
proxy you use and its configuration. The default settings are made to match and
work out of the box. If you need to change anything, be aware that the caching
proxy is configured separately from your PHP application and the
ResponseTagger - it is up to you to make sure the configurations match.
For example, the default configuration of Varnish
provided in this library uses the header
X-Cache-Tags with a
comma-separated list of tags. If you don’t change the
the header name, just instantiate the response tagger with its default settings:
use FOS\HttpCache\ResponseTagger; $responseTagger = new ResponseTagger();
If you need a different behavior, you can provide your own
TagHeaderFormatter instance. Don’t forget to also adjust your
proxy configuration to match the response. To use
xkey tags, instantiate the
CommaSeparatedTagHeaderFormatter yourself with the appropriate header and
glue, and pass it to the
use FOS\HttpCache\ResponseTagger; use FOS\HttpCache\TagHeaderFormatter; $formatter = new CommaSeparatedTagHeaderFormatter('xkey', ' '); $responseTagger = new ResponseTagger(['header_formatter' => $formatter]);
The response tagger validates tags that you set. By default, it simply ignores
empty strings and does not add them to the list of tags. You can set the
response tagger to strict mode to have it throw an
$responseTagger = new ResponseTagger(['strict' => true]);
With tags you can group related representations so it becomes easier to invalidate them. You will have to make sure your web application adds the correct tags on all responses. You can add tags to the response using:
Before any content is sent out, you need to send the tag header:
header(sprintf('%s: %s', $responseTagger->getTagsHeaderName(), $responseTagger->getTagsHeaderValue() )); $responseTagger->clear();
The call to
clear is only relevant if the same PHP process handles multiple
requests. This happens for example when you cache on user context
with the Symfony HttpCache.
If you are using Symfony with the FOSHttpCacheBundle, the tags
ResponseTagger are added to the response automatically.
You also have additional methods of defining tags with
annotations and on URL patterns.
Assume you sent four responses:
You can now invalidate some URLs using tags:
This will ban all requests having either the tag
In the above example, this will invalidate
/one will stay in the cache.