<?php
/*
* conditional.php:
* Support for HTTP conditional GET.
*
* Copyright (c) 2006 UK Citizens Online Democracy. All rights reserved.
* Email: chris@mysociety.org; WWW: http://www.mysociety.org/
*
* $Id: conditional.php,v 1.6 2007/09/19 17:32:43 matthew Exp $
*
*/
$cond_wkday_re = '(Sun|Mon|Tue|Wed|Thu|Fri|Sat)';
$cond_weekday_re = '(Sunday|Monday|Tuesday|Wednesday|Thursday|Friday|Saturday)';
$cond_month_re = '(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)';
$cond_month_map = array(
'Jan' => 1, 'Feb' => 2, 'Mar' => 3, 'Apr' => 4,
'May' => 5, 'Jun' => 6, 'Jul' => 7, 'Aug' => 8,
'Sep' => 9, 'Oct' => 10, 'Nov' => 11, 'Dec' => 12
);
$cond_date1_re = '(\d\d) ' . $cond_month_re . ' (\d\d\d\d)';
$cond_date2_re = '(\d\d)-' . $cond_month_re . '-(\d\d)';
$cond_date3_re = $cond_month_re . ' (\d\d| \d)';
$cond_time_re = '([01][0-9]|2[0-3]):([0-5][0-9]):([0-5][0-9]|6[012])';
/* XXX RFC 2616 prohibits seconds beyond 59, but presumably they will occur
* as leap seconds sometimes. */
/* cond_parse_http_date DATE
* Parse the supplied HTTP-style DATE, returning the number of seconds since
* the epoch that it represents, or null if it could not be parsed. */
function cond_parse_http_date($date) {
/* Unfortunately there is no strptime in PHP <5, so we must do this
* manually. */
$H = $M = $S = 0;
$Y = $m = $d = 0;
$ma = array();
global $cond_wkday_re, $cond_weekday_re, $cond_month_re, $cond_month_map,
$cond_date1_re, $cond_date2_re, $cond_date3_re, $cond_time_re;
if (preg_match("/^$cond_wkday_re, $cond_date1_re $cond_time_re GMT\$/", $date, $ma)) {
/* RFC 1123 */
$d = $ma[2];
$m = $cond_month_map[$ma[3]];
$Y = $ma[4];
$H = $ma[5];
$M = $ma[6];
$S = $ma[7];
} else if (preg_match("/^$cond_weekday_re, $cond_date2_re $cond_time_re GMT\$/", $date, $ma)) {
/* RFC 850 */
$d = $ma[2];
$m = $cond_month_map[$ma[3]];
$Y = $ma[4] + ($ma[4] < 50 ? 2000 : 1900); /* XXX */
$H = $ma[5];
$M = $ma[6];
$S = $ma[7];
} else if (preg_match("/^$cond_wkday_re $cond_date3_re $cond_time_re (\\d{4})\$/", $date, $ma)) {
/* asctime(3) */
$d = preg_replace('/ /', '', $ma[3]);
$m = $cond_month_map[$ma[2]];
$Y = $ma[7];
$H = $ma[4];
$M = $ma[5];
$S = $ma[6];
} else
return null;
return gmmktime($H, $M, $S, $m, $d, $Y);
}
/* cond_quote_etag ETAG
* Return a quoted copy of ETAG suitable for including in an ETag: header. */
function cond_quote_etag($etag) {
return '"' . preg_replace('/([\\"])/', '\\\\$1', $etag) . '"';
}
/* cond_headers TIME [ETAG]
* Send Last-Modified: and ETag: headers. The ETAG is assumed to be a weak
* one. */
function cond_headers($time, $etag = null) {
if (isset($time))
header('Last-Modified: ' . gmstrftime('%a, %d %b %Y %H:%M:%S GMT', $time));
if (isset($etag))
header('ETag: W/' . cond_quote_etag($etag));
}
/* cond_304 TIME [ETAG]
* Do a 304 Not Modified response. */
function cond_304($time, $etag = null) {
header('Status: 304 Not Modified');
cond_headers($time, $etag);
}
/* cond_maybe_respond TIME [ETAG]
* If the client has indicated that they already have a page modified at or
* after the given last-modified TIME, or one which matches the supplied ETAG,
* then generate an appropriate 304 Not Modified response and return true;
* otherwise, return false. Either TIME or ETAG may be null if a last-modified
* time or entity tag are not available for this page. ETAG is assumed to be
* a weak etag if it is supplied. */
function cond_maybe_respond($time, $etag = null) {
if (!array_key_exists('REQUEST_METHOD', $_SERVER)
&& $_SERVER['REQUEST_METHOD'] != 'GET'
&& $_SERVER['REQUEST_METHOD'] != 'HEAD')
return false;
$check_etag = (isset($etag) && array_key_exists('HTTP_IF_NONE_MATCH', $_SERVER));
$check_ims = (isset($time) && array_key_exists('HTTP_IF_MODIFIED_SINCE', $_SERVER));
if ($check_etag && $check_ims) {
if (cond_if_modified_since($time) && cond_if_none_match($etag)) {
cond_304($time, $etag);
return true;
}
} elseif ($check_etag) {
if (cond_if_none_match($etag)) {
cond_304($time, $etag);
return true;
}
} elseif ($check_ims) {
if (cond_if_modified_since($time)) {
cond_304($time, $etag);
return true;
}
}
return false;
}
function cond_if_modified_since($time) {
$t = cond_parse_http_date($_SERVER['HTTP_IF_MODIFIED_SINCE']);
if (isset($t) && $t >= $time)
return true;
return false;
}
function cond_if_none_match($etag) {
if ($_SERVER['HTTP_IF_NONE_MATCH'] == '*') return true;
$etags = preg_split('/\s*,\s*/', $_SERVER['HTTP_IF_NONE_MATCH']);
$q = 'W/' . cond_quote_etag($etag);
foreach ($etags as $q2) {
if ($q2 == $q) {
return true;
}
}
return false;
}
?>
