(PECL pecl_http >= 0.1.0)
http_cache_last_modified — Caching by last modification
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 设定 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() 和 http_send_stream().
Unix timestamp
Returns FALSE or exits on success with 304 Not Modified if the entity is cached. See the INI 设定 http.force_exit for what "exits" means.
Example #1 A http_cache_last_modified() example
Caching for 5 seconds.
<?php
http_cache_last_modified(-5);
printf("%s\n", http_date());
?>