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<?php defined('SYSPATH') or die('No direct script access.');
/**
* Controls headers that effect client caching of pages
*
* $Id: expires.php 1970 2008-02-06 21:54:29Z Shadowhand $
*
* @package Expires Helper
* @author Kohana Team
* @copyright (c) 2007-2008 Kohana Team
* @license http://kohanaphp.com/license.html
*/
class expires {

/**
* Sets the amount of time before a page expires
*
* @param integer Seconds before the page expires
* @return boolean
*/
public static function set($seconds = 60)
{
if (expires::check_headers())
{
$now = $expires = time();

// Set the expiration timestamp
$expires += $seconds;

// Send headers
header('Last-Modified: '.gmdate('D, d M Y H:i:s', $now).' GMT');
header('Expires: '.gmdate('D, d M Y H:i:s', $expires).' GMT');
header('Cache-Control: max-age='.$seconds);

return $expires;
}

return FALSE;
}

/**
* Checks to see if a page should be updated or send Not Modified status
*
* @param integer Seconds added to the modified time received to calculate what should be sent
* @return bool FALSE when the request needs to be updated
*/
public static function check($seconds = 60)
{
if ( ! empty($_SERVER['HTTP_IF_MODIFIED_SINCE']) AND expires::check_headers())
{
if (strpos($_SERVER['HTTP_IF_MODIFIED_SINCE'], ';') !== FALSE)
{
// IE6 and perhaps other IE versions send length too, compensate here
$mod_time = preg_replace('/^(.+?);/', '$1', $_SERVER['HTTP_IF_MODIFIED_SINCE']);
}
else
{
$mod_time = $_SERVER['HTTP_IF_MODIFIED_SINCE'];
}

$current_time = time();

$mod_time = strtotime($mod_time);
$mod_time_diff = $mod_time + $seconds - $current_time;

if ($mod_time_diff > 0)
{
// Re-send headers
header('Last-Modified: '.gmdate('D, d M Y H:i:s', $mod_time).' GMT');
header('Expires: '.gmdate('D, d M Y H:i:s', $current_time + $mod_time_diff).' GMT');
header('Cache-Control: max-age='.$mod_time_diff);
header('Status: 304 Not Modified', TRUE, 304);

// Prevent any output
Event::add('system.display', array('expires', 'prevent_output'));

// Exit to prevent other output
exit;
}
}

return FALSE;
}

/**
* Check headers already created to not step on download or Img_lib's feet
*
* @return boolean
*/
public static function check_headers()
{
foreach (headers_list() as $header)
{
if (stripos($header, 'Last-Modified:') === 0 OR stripos($header, 'Expires:') === 0)
{
return FALSE;
}
}

return TRUE;
}

/**
* Prevent any output from being displayed. Executed during system.display.
*
* @return void
*/
public static function prevent_output()
{
Kohana::$output = '';
}

} // End expires
(12-12/36)