php man page for http_cache_etag

HTTP_CACHE_ETAG(3)							 1							HTTP_CACHE_ETAG(3)

http_cache_etag - Caching by ETag

SYNOPSIS
       bool http_cache_etag ([string  $etag])

DESCRIPTION
	Attempts  to  cache  the  sent	entity	by  its  ETag,	either	supplied  or  generated  by  the  hash algorithm specified by the INI set-
       tinghttp.etag.mode.

	If the clients If-None-Match header matches the supplied/calculated ETag, the body is considered cached on the clients side and a 304  Not
       Modified status code is issued.

	A log entry is written to the cache log if the INI settinghttp.log.cache is set and the cache attempt was successful.

       Note

	      This function may be used in conjunction with http_send_data(3), http_send_file(3) and http_send_stream(3).

	If this function is used outside the http_send_*() API, it facilitates the ob_etaghandler(3).

PARAMETERS
	      o $etag
		- custom ETag

RETURN VALUES
	Returns  FALSE	or  exits  on  success	with 304 Not Modified if the entity is cached. See the INI settinghttp.force_exit for what "exits"
       means.

EXAMPLES
       Example #1

	      A http_cache_etag(3) example

	      <?php
	      http_cache_etag();
	      http_send_data("data");
	      ?>

SEE ALSO
       http_cache_last_modified(3), ob_etaghandler(3), http_match_etag(3), the HttpResponse class if you are using PHP 5.1.0 and above.

PHP Documentation Group 													HTTP_CACHE_ETAG(3)