php man page for http_cache_last_modified

HTTP_CACHE_LAST_MODIFIED(3)						 1					       HTTP_CACHE_LAST_MODIFIED(3)

http_cache_last_modified - Caching by last modification

SYNOPSIS
       bool http_cache_last_modified ([int  $timestamp_or_expires])

DESCRIPTION
	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 omit-
       ted, 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 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).

PARAMETERS
	      o $timestamp_or_expires
		- Unix timestamp

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_last_modified(3) example

	       Caching for 5 seconds.

	      <?php
	      http_cache_last_modified(-5);
	      printf("%s
", http_date());
	      ?>

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

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