<?php

/**

* Signals via headers that page should not be cached at all

*/

function noCache(){

header('Expires: '.date("D, d M Y H:i:s").' GMT', true);

header('Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0', true);

header('Pragma: no-cache', true);

}

/**

* Signals via headers that the page should be cached for a certain amount of seconds

* @param int $seconds Seconds how long the page should be cached

* @param bool $private If true only the client is allowed to cached, proxies not (default false)

*/

function setCache($seconds=0, $private=false){

if(!$seconds || !is_int($seconds) || $seconds<=0){ noCache(); return true; }

header("Cache-Control: ".($private ? "private" : "public").", max-age=".$seconds, true);

}

/**

* Signals via headers that the page should be cached until a given UTC time in seconds

* @param int $timeUTCSec UTC time in seconds until page should be cached

* @param bool $private If true only the client is allowed to cached, proxies not (default false)

*/

function setCacheUntil($timeUTCSec, $private=false){

setCache($timeUTCSec-time(), $private);

}

/**

* Signals via headers that the page should be cached until the next full given unit (e.g. until the next full hour)

* @param int $unitSeconds Seconds defining the unit interval (e.g. 3600 for hourly)

* @param bool $private If true only the client is allowed to cached, proxies not (default false)

*/

function setCacheUntilFullUnit($unitSeconds=3600, $private=false){

$time = time();

setCache((intval($time / $unitSeconds) + 1)*$unitSeconds - $time, $private);

}

?>