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<?php defined('SYSPATH') or die('No direct script access.');
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/**
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* Controls headers that effect client caching of pages
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*
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* $Id: expires.php 1970 2008-02-06 21:54:29Z Shadowhand $
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*
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* @package Expires Helper
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* @author Kohana Team
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* @copyright (c) 2007-2008 Kohana Team
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* @license http://kohanaphp.com/license.html
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*/
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class expires {
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/**
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* Sets the amount of time before a page expires
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*
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* @param integer Seconds before the page expires
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* @return boolean
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*/
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public static function set($seconds = 60)
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{
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if (expires::check_headers())
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{
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$now = $expires = time();
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// Set the expiration timestamp
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$expires += $seconds;
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// Send headers
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header('Last-Modified: '.gmdate('D, d M Y H:i:s', $now).' GMT');
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header('Expires: '.gmdate('D, d M Y H:i:s', $expires).' GMT');
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header('Cache-Control: max-age='.$seconds);
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return $expires;
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}
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return FALSE;
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}
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/**
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* Checks to see if a page should be updated or send Not Modified status
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*
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* @param integer Seconds added to the modified time received to calculate what should be sent
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* @return bool FALSE when the request needs to be updated
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*/
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public static function check($seconds = 60)
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{
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if ( ! empty($_SERVER['HTTP_IF_MODIFIED_SINCE']) AND expires::check_headers())
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{
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if (strpos($_SERVER['HTTP_IF_MODIFIED_SINCE'], ';') !== FALSE)
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{
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// IE6 and perhaps other IE versions send length too, compensate here
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$mod_time = preg_replace('/^(.+?);/', '$1', $_SERVER['HTTP_IF_MODIFIED_SINCE']);
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}
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else
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{
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$mod_time = $_SERVER['HTTP_IF_MODIFIED_SINCE'];
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}
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$current_time = time();
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$mod_time = strtotime($mod_time);
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$mod_time_diff = $mod_time + $seconds - $current_time;
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if ($mod_time_diff > 0)
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{
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// Re-send headers
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header('Last-Modified: '.gmdate('D, d M Y H:i:s', $mod_time).' GMT');
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header('Expires: '.gmdate('D, d M Y H:i:s', $current_time + $mod_time_diff).' GMT');
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header('Cache-Control: max-age='.$mod_time_diff);
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header('Status: 304 Not Modified', TRUE, 304);
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// Prevent any output
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Event::add('system.display', array('expires', 'prevent_output'));
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// Exit to prevent other output
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exit;
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}
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}
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return FALSE;
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}
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/**
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* Check headers already created to not step on download or Img_lib's feet
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*
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* @return boolean
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*/
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public static function check_headers()
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{
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foreach (headers_list() as $header)
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{
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if (stripos($header, 'Last-Modified:') === 0 OR stripos($header, 'Expires:') === 0)
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{
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return FALSE;
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}
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}
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return TRUE;
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}
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/**
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* Prevent any output from being displayed. Executed during system.display.
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*
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* @return void
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*/
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public static function prevent_output()
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{
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Kohana::$output = '';
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}
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} // End expires
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