http_cache_etag
http_chunked_decode
HTTP Functions
PHP Manual

# http_cache_last_modified

Caching by last modification

### Description

bool http_cache_last_modified ([ 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.

> Note: This function may be used in conjunction with http_send_data, http_send_file and http_send_stream.

### Parameters

`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 setting http.force_exit for what "exits" means.

### Examples

Example #1 A http_cache_last_modified example

Caching for 5 seconds.

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

### See Also

- http_cache_etag
- the HttpResponse class if you are using PHP 5.1.0 and above