## 例

`

     bool http_cache_etag ([ string $etag ] )

`

## 説明

Attempts to cache the sent entity by its ETag, either supplied or generated by the hash algorithm specified by the INI setting http.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 setting http.log.cache is set and the cache attempt was successful. Note: This function may be used in conjunction with http_send_data(), http_send_file() and http_send_stream(). If this function is used outside the http_send_*() API, it facilitates the ob_etaghandler().

## 戻り値

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