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+<?php
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+/*
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+ Enable support for HTTP/1.x conditional requests in PHP.
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+ Goal: Optimisation
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+ - If the client sends a HEAD request, avoid transferring data and return the correct headers.
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+ - If the client already has the same version in its cache, avoid transferring data again (304 Not Modified).
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+ - Possibility to control cache for client and proxies (public or private policy, life time).
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+ - When $feedMode is set to true, in the case of a RSS/ATOM feed,
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+ it puts a timestamp in the global variable $clientCacheDate to allow the sending of only the articles newer than the client's cache.
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+ - When $compression is set to true, compress the data before sending it to the client and persitent connections are allowed.
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+ - When $session is set to true, automatically checks if $_SESSION has been modified during the last generation the document.
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+
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+ Interface:
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+ - function httpConditional($UnixTimeStamp,$cacheSeconds=0,$cachePrivacy=0,$feedMode=false,$compression=false)
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+ [Required] $UnixTimeStamp: Date of the last modification of the data to send to the client (Unix Timestamp format).
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+ [Implied] $cacheSeconds=0: Lifetime in seconds of the document. If $cacheSeconds<0, cache is disabled. If $cacheSeconds==0, the document will be revalidated each time it is accessed. If $cacheSeconds>0, the document will be cashed and not revalidated against the server for this delay.
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+ [Implied] $cachePrivacy=0: 0=private, 1=normal (public), 2=forced public. When public, it allows a cashed document ($cacheSeconds>0) to be shared by several users.
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+ [Implied] $feedMode=false: Special RSS/ATOM feeds. When true, it sets $cachePrivacy to 0 (private), does not use the modification time of the script itself, and puts the date of the client's cache (or a old date from 1980) in the global variable $clientCacheDate.
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+ [implied] $compression=false: Enable the compression and allows persistant connections (automatic detection of the capacities of the client).
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+ [implied] $session=false: To be turned on when sessions are used. Checks if the data contained in $_SESSION has been modified during the last generation the document.
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+ Returns: True if the connection can be closed (e.g.: the client has already the lastest version), false if the new content has to be send to the client.
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+
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+ Typical use:
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+ <?php
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+ require_once('http-conditional.php');
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+ //Date of the last modification of the content (Unix Timestamp format).
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+ //Examples: query the database, or last modification of a static file.
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+ $dateLastModification=...;
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+ if (httpConditional($dateLastModification))
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+ {
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+ ... //Close database connections, and other cleaning.
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+ exit(); //No need to send anything
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+ }
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+ //Do not send any text to the client before this line.
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+ ... //Rest of the script, just as you would do normally.
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+ ?>
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+
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+ Version 1.6.2a, 2008-03-06, http://alexandre.alapetite.fr/doc-alex/php-http-304/
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+
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+ ------------------------------------------------------------------
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+ Written by Alexandre Alapetite, http://alexandre.alapetite.fr/cv/
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+
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+ Copyright 2004-2008, Licence: Creative Commons "Attribution-ShareAlike 2.0 France" BY-SA (FR),
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+ http://creativecommons.org/licenses/by-sa/2.0/fr/
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+ http://alexandre.alapetite.fr/divers/apropos/#by-sa
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+ - Attribution. You must give the original author credit
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+ - Share Alike. If you alter, transform, or build upon this work,
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+ you may distribute the resulting work only under a license identical to this one
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+ (Can be included in GPL/LGPL projects)
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+ - The French law is authoritative
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+ - Any of these conditions can be waived if you get permission from Alexandre Alapetite
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+ - Please send to Alexandre Alapetite the modifications you make,
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+ in order to improve this file for the benefit of everybody
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+
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+ If you want to distribute this code, please do it as a link to:
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+ http://alexandre.alapetite.fr/doc-alex/php-http-304/
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+*/
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+
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+//In RSS/ATOM feedMode, contains the date of the clients last update.
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+$clientCacheDate=0; //Global public variable because PHP4 does not allow conditional arguments by reference
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+$_sessionMode=false; //Global private variable
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+
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+function httpConditional($UnixTimeStamp,$cacheSeconds=0,$cachePrivacy=0,$feedMode=false,$compression=false,$session=false)
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+{//Credits: http://alexandre.alapetite.fr/doc-alex/php-http-304/
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+ //RFC2616 HTTP/1.1: http://www.w3.org/Protocols/rfc2616/rfc2616.html
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+ //RFC1945 HTTP/1.0: http://www.w3.org/Protocols/rfc1945/rfc1945.txt
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+
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+ if (headers_sent()) return false;
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+
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+ if (isset($_SERVER['SCRIPT_FILENAME'])) $scriptName=$_SERVER['SCRIPT_FILENAME'];
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+ elseif (isset($_SERVER['PATH_TRANSLATED'])) $scriptName=$_SERVER['PATH_TRANSLATED'];
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+ else return false;
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+
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+ if ((!$feedMode)&&(($modifScript=filemtime($scriptName))>$UnixTimeStamp))
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+ $UnixTimeStamp=$modifScript;
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+ $UnixTimeStamp=min($UnixTimeStamp,time());
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+ $is304=true;
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+ $is412=false;
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+ $nbCond=0;
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+
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+ //rfc2616-sec3.html#sec3.3.1
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+ $dateLastModif=gmdate('D, d M Y H:i:s \G\M\T',$UnixTimeStamp);
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+ $dateCacheClient='Thu, 10 Jan 1980 20:30:40 GMT';
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+
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+ //rfc2616-sec14.html#sec14.19 //='"0123456789abcdef0123456789abcdef"'
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+ if (isset($_SERVER['QUERY_STRING'])) $myQuery='?'.$_SERVER['QUERY_STRING'];
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+ else $myQuery='';
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+ if ($session&&isset($_SESSION))
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+ {
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+ global $_sessionMode;
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+ $_sessionMode=$session;
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+ $myQuery.=print_r($_SESSION,true).session_name().'='.session_id();
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+ }
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+ $etagServer='"'.md5($scriptName.$myQuery.'#'.$dateLastModif).'"';
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+
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+ if ((!$is412)&&isset($_SERVER['HTTP_IF_MATCH']))
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+ {//rfc2616-sec14.html#sec14.24
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+ $etagsClient=stripslashes($_SERVER['HTTP_IF_MATCH']);
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+ $is412=(($etagClient!='*')&&(strpos($etagsClient,$etagServer)===false));
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+ }
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+ if ($is304&&isset($_SERVER['HTTP_IF_MODIFIED_SINCE']))
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+ {//rfc2616-sec14.html#sec14.25 //rfc1945.txt
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+ $nbCond++;
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+ $dateCacheClient=$_SERVER['HTTP_IF_MODIFIED_SINCE'];
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+ $p=strpos($dateCacheClient,';');
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+ if ($p!==false)
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+ $dateCacheClient=substr($dateCacheClient,0,$p);
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+ $is304=($dateCacheClient==$dateLastModif);
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+ }
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+ if ($is304&&isset($_SERVER['HTTP_IF_NONE_MATCH']))
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+ {//rfc2616-sec14.html#sec14.26
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+ $nbCond++;
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+ $etagClient=stripslashes($_SERVER['HTTP_IF_NONE_MATCH']);
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+ $is304=(($etagClient==$etagServer)||($etagClient=='*'));
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+ }
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+ if ((!$is412)&&isset($_SERVER['HTTP_IF_UNMODIFIED_SINCE']))
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+ {//rfc2616-sec14.html#sec14.28
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+ $dateCacheClient=$_SERVER['HTTP_IF_UNMODIFIED_SINCE'];
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+ $p=strpos($dateCacheClient,';');
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+ if ($p!==false)
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+ $dateCacheClient=substr($dateCacheClient,0,$p);
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+ $is412=($dateCacheClient!=$dateLastModif);
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+ }
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+ if ($feedMode)
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+ {//Special RSS/ATOM
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+ global $clientCacheDate;
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+ $clientCacheDate=strtotime($dateCacheClient);
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+ $cachePrivacy=0;
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+ }
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+
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+ if ($is412)
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+ {//rfc2616-sec10.html#sec10.4.13
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+ header('HTTP/1.1 412 Precondition Failed');
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+ header('Cache-Control: private, max-age=0, must-revalidate');
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+ header('Content-Type: text/plain');
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+ echo "HTTP/1.1 Error 412 Precondition Failed: Precondition request failed positive evaluation\n";
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+ return true;
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+ }
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+ elseif ($is304&&($nbCond>0))
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+ {//rfc2616-sec10.html#sec10.3.5
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+ header('HTTP/1.0 304 Not Modified');
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+ header('Etag: '.$etagServer);
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+ if ($feedMode) header('Connection: close'); //Comment this line under IIS
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+ return true;
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+ }
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+ else
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+ {//rfc2616-sec10.html#sec10.2.1
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+ //rfc2616-sec14.html#sec14.3
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+ if ($compression) ob_start('_httpConditionalCallBack'); //Will check HTTP_ACCEPT_ENCODING
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+ //header('HTTP/1.0 200 OK');
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+ if ($cacheSeconds<0)
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+ {
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+ $cache='private, no-cache, no-store, must-revalidate';
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+ header('Pragma: no-cache');
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+ }
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+ else
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+ {
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+ if ($cacheSeconds==0) $cache='private, must-revalidate, ';
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+ elseif ($cachePrivacy==0) $cache='private, ';
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+ elseif ($cachePrivacy==2) $cache='public, ';
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+ else $cache='';
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+ $cache.='max-age='.floor($cacheSeconds);
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+ }
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+ //header('Expires: '.gmdate('D, d M Y H:i:s \G\M\T',time()+$cacheSeconds)); //HTTP/1.0 //rfc2616-sec14.html#sec14.21
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+ header('Cache-Control: '.$cache); //rfc2616-sec14.html#sec14.9
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+ header('Last-Modified: '.$dateLastModif);
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+ header('Etag: '.$etagServer);
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+ if ($feedMode) header('Connection: close'); //rfc2616-sec14.html#sec14.10 //Comment this line under IIS
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+ return $_SERVER['REQUEST_METHOD']=='HEAD'; //rfc2616-sec9.html#sec9.4
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+ }
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+}
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+
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+function _httpConditionalCallBack($buffer,$mode=5)
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+{//Private function automatically called at the end of the script when compression is enabled
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+ //rfc2616-sec14.html#sec14.11
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+ //You can adjust the level of compression with zlib.output_compression_level in php.ini
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+ if (extension_loaded('zlib')&&(!ini_get('zlib.output_compression')))
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+ {
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+ $buffer2=ob_gzhandler($buffer,$mode); //Will check HTTP_ACCEPT_ENCODING and put correct headers such as Vary //rfc2616-sec14.html#sec14.44
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+ if (strlen($buffer2)>1) //When ob_gzhandler succeeded
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+ $buffer=$buffer2;
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+ }
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+ header('Content-Length: '.strlen($buffer)); //Allows persistant connections //rfc2616-sec14.html#sec14.13
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+ return $buffer;
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+}
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+
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+function httpConditionalRefresh($UnixTimeStamp)
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+{//Update HTTP headers if the content has just been modified by the client's request
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+ //See an example on http://alexandre.alapetite.fr/doc-alex/compteur/
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+ if (headers_sent()) return false;
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+
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+ if (isset($_SERVER['SCRIPT_FILENAME'])) $scriptName=$_SERVER['SCRIPT_FILENAME'];
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+ elseif (isset($_SERVER['PATH_TRANSLATED'])) $scriptName=$_SERVER['PATH_TRANSLATED'];
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+ else return false;
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+
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+ $dateLastModif=gmdate('D, d M Y H:i:s \G\M\T',$UnixTimeStamp);
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+
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+ if (isset($_SERVER['QUERY_STRING'])) $myQuery='?'.$_SERVER['QUERY_STRING'];
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+ else $myQuery='';
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+ global $_sessionMode;
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+ if ($_sessionMode&&isset($_SESSION))
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+ $myQuery.=print_r($_SESSION,true).session_name().'='.session_id();
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+ $etagServer='"'.md5($scriptName.$myQuery.'#'.$dateLastModif).'"';
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+
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+ header('Last-Modified: '.$dateLastModif);
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+ header('Etag: '.$etagServer);
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+}
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Alexandre Alapetite