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<?php defined('SYSPATH') OR die('No direct access allowed.');
/**
* Controls headers that effect client caching of pages
*
* $Id: expires.php 4679 2009-11-10 01:45:52Z isaiah $
*
* @package Core
* @author Kohana Team
* @copyright (c) 2007-2009 Kohana Team
* @license http://kohanaphp.com/license
*/
class expires_Core {
/**
* Sets the amount of time before content expires
*
* @param integer Seconds before the content expires
* @return integer Timestamp when the content expires
*/
public static function set($seconds = 60)
{
$now = time();
$expires = $now + $seconds;
header('Last-Modified: '.gmdate('D, d M Y H:i:s T', $now));
// HTTP 1.0
header('Expires: '.gmdate('D, d M Y H:i:s T', $expires));
// HTTP 1.1
header('Cache-Control: max-age='.$seconds);
return $expires;
}
/**
* Parses the If-Modified-Since header
*
* @return integer|boolean Timestamp or FALSE when header is lacking or malformed
*/
public static function get()
{
if ( ! empty($_SERVER['HTTP_IF_MODIFIED_SINCE']))
{
// Some versions of IE6 append "; length=####"
if (($strpos = strpos($_SERVER['HTTP_IF_MODIFIED_SINCE'], ';')) !== FALSE)
{
$mod_time = substr($_SERVER['HTTP_IF_MODIFIED_SINCE'], 0, $strpos);
}
else
{
$mod_time = $_SERVER['HTTP_IF_MODIFIED_SINCE'];
}
return strtotime($mod_time);
}
return FALSE;
}
/**
* Checks to see if content should be updated otherwise sends Not Modified status
* and exits.
*
* @uses exit()
* @uses expires::get()
*
* @param integer Maximum age of the content in seconds
* @return integer|boolean Timestamp of the If-Modified-Since header or FALSE when header is lacking or malformed
*/
public static function check($seconds = 60)
{
if ($last_modified = expires::get())
{
$expires = $last_modified + $seconds;
$max_age = $expires - time();
if ($max_age > 0)
{
// Content has not expired
header($_SERVER['SERVER_PROTOCOL'].' 304 Not Modified');
header('Last-Modified: '.gmdate('D, d M Y H:i:s T', $last_modified));
// HTTP 1.0
header('Expires: '.gmdate('D, d M Y H:i:s T', $expires));
// HTTP 1.1
header('Cache-Control: max-age='.$max_age);
// Clear any output
Event::add('system.display', create_function('', 'Kohana::$output = "";'));
exit;
}
}
return $last_modified;
}
/**
* Check if expiration headers are already set
*
* @return boolean
*/
public static function headers_set()
{
foreach (headers_list() as $header)
{
if (strncasecmp($header, 'Expires:', 8) === 0
OR strncasecmp($header, 'Cache-Control:', 14) === 0
OR strncasecmp($header, 'Last-Modified:', 14) === 0)
{
return TRUE;
}
}
return FALSE;
}
} // End expires
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