system/helpers/expires.php

   1 <?php defined('SYSPATH') OR die('No direct access allowed.');
   2 /**
   3  * Controls headers that effect client caching of pages
   4  *
   5  * $Id: expires.php 3917 2009-01-21 03:06:22Z zombor $
   6  *
   7  * @package    Core
   8  * @author     Kohana Team
   9  * @copyright  (c) 2007-2008 Kohana Team
  10  * @license    http://kohanaphp.com/license.html
  11  */
  12 class expires {
  13
  14         /**
  15          * Sets the amount of time before a page expires
  16          *
  17          * @param  integer Seconds before the page expires
  18          * @return boolean
  19          */
  20         public static function set($seconds = 60)
  21         {
  22                 if (expires::check_headers())
  23                 {
  24                         $now = $expires = time();
  25
  26                         // Set the expiration timestamp
  27                         $expires += $seconds;
  28
  29                         // Send headers
  30                         header('Last-Modified: '.gmdate('D, d M Y H:i:s T', $now));
  31                         header('Expires: '.gmdate('D, d M Y H:i:s T', $expires));
  32                         header('Cache-Control: max-age='.$seconds);
  33
  34                         return $expires;
  35                 }
  36
  37                 return FALSE;
  38         }
  39
  40         /**
  41          * Checks to see if a page should be updated or send Not Modified status
  42          *
  43          * @param   integer  Seconds added to the modified time received to calculate what should be sent
  44          * @return  bool     FALSE when the request needs to be updated
  45          */
  46         public static function check($seconds = 60)
  47         {
  48                 if ( ! empty($_SERVER['HTTP_IF_MODIFIED_SINCE']) AND expires::check_headers())
  49                 {
  50                         if (($strpos = strpos($_SERVER['HTTP_IF_MODIFIED_SINCE'], ';')) !== FALSE)
  51                         {
  52                                 // IE6 and perhaps other IE versions send length too, compensate here
  53                                 $mod_time = substr($_SERVER['HTTP_IF_MODIFIED_SINCE'], 0, $strpos);
  54                         }
  55                         else
  56                         {
  57                                 $mod_time = $_SERVER['HTTP_IF_MODIFIED_SINCE'];
  58                         }
  59
  60                         $mod_time = strtotime($mod_time);
  61                         $mod_time_diff = $mod_time + $seconds - time();
  62
  63                         if ($mod_time_diff > 0)
  64                         {
  65                                 // Re-send headers
  66                                 header('Last-Modified: '.gmdate('D, d M Y H:i:s T', $mod_time));
  67                                 header('Expires: '.gmdate('D, d M Y H:i:s T', time() + $mod_time_diff));
  68                                 header('Cache-Control: max-age='.$mod_time_diff);
  69                                 header('Status: 304 Not Modified', TRUE, 304);
  70
  71                                 // Prevent any output
  72                                 Event::add('system.display', array('expires', 'prevent_output'));
  73
  74                                 // Exit to prevent other output
  75                                 exit;
  76                         }
  77                 }
  78
  79                 return FALSE;
  80         }
  81
  82         /**
  83          * Check headers already created to not step on download or Img_lib's feet
  84          *
  85          * @return boolean
  86          */
  87         public static function check_headers()
  88         {
  89                 foreach (headers_list() as $header)
  90                 {
  91                         if (stripos($header, 'Last-Modified:') === 0 OR stripos($header, 'Expires:') === 0)
  92                         {
  93                                 return FALSE;
  94                         }
  95                 }
  96
  97                 return TRUE;
  98         }
  99
 100         /**
 101          * Prevent any output from being displayed. Executed during system.display.
 102          *
 103          * @return  void
 104          */
 105         public static function prevent_output()
 106         {
 107                 Kohana::$output = '';
 108         }
 109
 110 } // End expires