http_cache_last_modified -- Caching by last modification
( [int timestamp_or_expires] )
Attempts to cache the sent entity by its last modification date.
If the supplied argument is greater than 0, it is handled as timestamp
and will be sent as date of last modification. If it is 0 or omitted,
the current time will be sent as Last-Modified date.
If it's negative, it is handled as expiration time in seconds, which means
that if the requested last modification date is not between the calculated timespan,
the Last-Modified header is updated and the actual body will be sent.
A log entry will be written to the cache log if the INI setting
http.log.cache is set
and the cache attempt was successful.
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.
Example 1. A http_cache_last_modified() example
Caching for 5 seconds.