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<?php
/* vim: set expandtab tabstop=4 shiftwidth=4 softtabstop=4: */
/**
* HTTP::Header::Cache
*
* PHP versions 4 and 5
*
* @category HTTP
* @package HTTP_Header
* @author Wolfram Kriesing <wk@visionp.de>
* @author Michael Wallner <mike@php.net>
* @copyright 2003-2005 The Authors
* @license BSD, revised
* @version CVS: $Id: Cache.php 304418 2010-10-15 13:18:02Z clockwerx $
* @link http://pear.php.net/package/HTTP_Header
*/
/**
* Requires HTTP_Header
*/
require_once 'HTTP/Header.php';
/**
* HTTP_Header_Cache
*
* This package provides methods to easier handle caching of HTTP pages. That
* means that the pages can be cached at the client (user agent or browser) and
* your application only needs to send "hey client you already have the pages".
*
* Which is done by sending the HTTP-Status "304 Not Modified", so that your
* application load and the network traffic can be reduced, since you only need
* to send the complete page once. This is really an advantage e.g. for
* generated style sheets, or simply pages that do only change rarely.
*
* Usage:
* <code>
* require_once 'HTTP/Header/Cache.php';
* $httpCache = new HTTP_Header_Cache(4, 'weeks');
* $httpCache->sendHeaders();
* // your code goes here
* </code>
*
* @package HTTP_Header
* @category HTTP
* @access public
* @version $Revision: 304418 $
*/
class HTTP_Header_Cache extends HTTP_Header
{
/**
* Constructor
*
* Set the amount of time to cache.
*
* @access public
* @return object HTTP_Header_Cache
* @param int $expires
* @param string $unit
*/
function HTTP_Header_Cache($expires = 0, $unit = 'seconds')
{
parent::HTTP_Header();
$this->setHeader('Pragma', 'cache');
$this->setHeader('Last-Modified', $this->getCacheStart());
$this->setHeader('Cache-Control', 'private, must-revalidate, max-age=0');
if ($expires) {
if (!$this->isOlderThan($expires, $unit)) {
$this->exitCached();
}
$this->setHeader('Last-Modified', time());
}
}
/**
* Get Cache Start
*
* Returns the unix timestamp of the If-Modified-Since HTTP header or the
* current time if the header was not sent by the client.
*
* @access public
* @return int unix timestamp
*/
function getCacheStart()
{
if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && !$this->isPost()) {
return strtotime(current($array = explode(';',
$_SERVER['HTTP_IF_MODIFIED_SINCE'])));
}
return time();
}
/**
* Is Older Than
*
* You can call it like this:
* <code>
* $httpCache->isOlderThan(1, 'day');
* $httpCache->isOlderThan(47, 'days');
*
* $httpCache->isOlderThan(1, 'week');
* $httpCache->isOlderThan(3, 'weeks');
*
* $httpCache->isOlderThan(1, 'hour');
* $httpCache->isOlderThan(5, 'hours');
*
* $httpCache->isOlderThan(1, 'minute');
* $httpCache->isOlderThan(15, 'minutes');
*
* $httpCache->isOlderThan(1, 'second');
* $httpCache->isOlderThan(15);
* </code>
*
* If you specify something greater than "weeks" as time untit, it just
* works approximatly, because a month is taken to consist of 4.3 weeks.
*
* @access public
* @return bool Returns true if requested page is older than specified.
* @param int $time The amount of time.
* @param string $unit The unit of the time amount - (year[s], month[s],
* week[s], day[s], hour[s], minute[s], second[s]).
*/
function isOlderThan($time = 0, $unit = 'seconds')
{
if (!isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) || $this->isPost()) {
return true;
}
if (!$time) {
return false;
}
switch (strtolower($unit))
{
case 'year':
case 'years':
$time *= 12;
case 'month':
case 'months':
$time *= 4.3;
case 'week':
case 'weeks':
$time *= 7;
case 'day':
case 'days':
$time *= 24;
case 'hour':
case 'hours':
$time *= 60;
case 'minute':
case 'minutes':
$time *= 60;
}
return (time() - $this->getCacheStart()) > $time;
}
/**
* Is Cached
*
* Check whether we can consider to be cached on the client side.
*
* @access public
* @return bool Whether the page/resource is considered to be cached.
* @param int $lastModified Unix timestamp of last modification.
*/
function isCached($lastModified = 0)
{
if ($this->isPost()) {
return false;
}
if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && !$lastModified) {
return true;
}
if (!$seconds = time() - $lastModified) {
return false;
}
return !$this->isOlderThan($seconds);
}
/**
* Is Post
*
* Check if request method is "POST".
*
* @access public
* @return bool
*/
function isPost()
{
return isset($_SERVER['REQUEST_METHOD']) and
'POST' == $_SERVER['REQUEST_METHOD'];
}
/**
* Exit If Cached
*
* Exit with "HTTP 304 Not Modified" if we consider to be cached.
*
* @access public
* @return void
* @param int $lastModified Unix timestamp of last modification.
*/
function exitIfCached($lastModified = 0)
{
if ($this->isCached($lastModified)) {
$this->exitCached();
}
}
/**
* Exit Cached
*
* Exit with "HTTP 304 Not Modified".
*
* @access public
* @return void
*/
function exitCached()
{
$this->sendHeaders();
$this->sendStatusCode(304);
exit;
}
/**
* Set Last Modified
*
* @access public
* @return void
* @param int $lastModified The unix timestamp of last modification.
*/
function setLastModified($lastModified = null)
{
$this->setHeader('Last-Modified', $lastModified);
}
}
?>
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