<?php
##############################################################################
#     XHTML and mimetype script for PHP                                      #
#     Copyright (C) 2007  Darrin Yeager                                      #
#     http://www.dyeager.org                                                 #
#                                                                            #
#   Version 2.0                                                              #
#                                                                            #
#    Changes:                                                                #
#       1. Checks Last-Modified header as well as ETag.                      #
#       2. Uses variable $max_age_hours to easily change cache time.         #
#       3. Allows HTML Strict doctype, and doesn't send Vary:Accept          #
#           header for HTML as it isn't needed (it's always text/html).      #
#       4. Sends XML prolog for application/xhtml+xml mimetypes.             #
#       5. Minor changes in headers to more comform to HTTP specs.           #
#                                                                            #
# Redistribution and use in source and binary forms, with or without         #
# modification, are permitted provided that the following conditions         #
# are met:                                                                   #
#                                                                            #
#   1. Redistributions of source code must retain the above copyright        #
#      notice, this list of conditions and the following disclaimer.         #
#                                                                            #
#   2. Redistributions in binary form must reproduce the above copyright     #
#      notice, this list of conditions and the following disclaimer in the   #
#      documentation and/or other materials provided with the distribution.  #
#                                                                            #
#   3. Redistributions of modified versions must carry prominent notices     #
#      stating that you changed the files and the date of any change.        #
#                                                                            #
#   4. Neither the name of Darrin Yeager nor the names of any contributors   #
#      may be used to endorse or promote products derived from this software #
#      without specific prior written permission.                            #
#                                                                            #
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS        #
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT          #
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR      #
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT       #
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,      #
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED   #
# TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR     #
# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF     #
# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING       #
# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS         #
# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.               #
##############################################################################
#
# Change this if you're using something other than UTF-8 (which you really shouldn't)
$charset = "utf-8";
# Change this age if you want your pages to expire earlier or later than 1 day.
$max_age_hours = 24;

#Nothing to modify below this line.
$mime = "text/html";
$is304 = false;


if (! defined("DOCTYPE"))
	define("DOCTYPE","strict");

# NOTE: To allow for q-values with one space (text/html; q=0.5),
# use the following regex:
# "/text\/html;[\ ]{0,1}q=([0-1]{0,1}\.\d{0,4})/i"
if (DOCTYPE !== "html-strict") { //if using HTML Doctype we can't send as application/xhtml+xml 
	if((isset($_SERVER["HTTP_ACCEPT"])) && (stristr($_SERVER["HTTP_ACCEPT"],"application/xhtml+xml")))  {
		if(preg_match("/application\/xhtml\+xml;q=([0-1]{0,1}\.\d{0,4})/i",$_SERVER["HTTP_ACCEPT"],$matches)) {
			$xhtml_q = $matches[1];
			if(preg_match("/text\/html;q=([0-1]{0,1}\.\d{0,4})/i",$_SERVER["HTTP_ACCEPT"],$matches)) {
				$html_q = $matches[1];
				if((float)$xhtml_q >= (float)$html_q)
					$mime = "application/xhtml+xml";
			}
		}
		else
			$mime = "application/xhtml+xml";
	}
}

# Get the file stats and compute last-modified time.
$filestats = @stat($_SERVER["SCRIPT_FILENAME"]);
$lastmod = $filestats[9] - date('Z');  #Convert Local time -> GMT
$lastmodified = date("D, d M Y H:i:s", $lastmod) . " GMT";

# ETag is "inode-lastmodtime-filesize" - See PHP stat function for more detail
$etag = '"' . dechex($filestats[1]) . "-" . dechex($lastmod) . "-" . dechex($filestats[7]) . '"';

# Check HTTP_IF_NONE_MATCH
# and report a 304 Not Modified header if they match.
if (isset ($_SERVER["HTTP_IF_NONE_MATCH"])) {
	if ($etag === stripslashes($_SERVER["HTTP_IF_NONE_MATCH"])) 
		$is304 = true;
}

# Check HTTP_IF_MODIFIED_SINCE
# and report a 304 Not Modified header if they match.
if ((isset ($_SERVER["HTTP_IF_MODIFIED_SINCE"]))) {
	#Old Netscape and/or IE can put "; length=xyz" after the "GMT" in date
	#which completly violates the specs, so we have to strip it out.
	if (preg_replace('/;.*$/', '', $_SERVER["HTTP_IF_MODIFIED_SINCE"]) === $lastmodified)
		$is304 = true;
}

# Get max age in seconds.
$max_age = $max_age_hours * 60 * 60;

header("Cache-Control: max-age=$max_age, s-maxage=$max_age");
header("Expires: " . date("D, d M Y H:i:s",time() + $max_age - date('Z')) . " GMT");
if (DOCTYPE !== "html-strict")
	header("Vary: Accept");
# If for some reason we didn't get a valid file modification time
# from the stat function, or it errored out, DO NOT send the ETag
# header as it will not be valid. Valid in this since is defined
# as modified AFTER Dec 24, 1999.
if ($lastmod > 946080000) { 	# 946080000 = Dec 24, 1999 4PM
	header("ETag: " . $etag);
	header("Last-Modified: " . $lastmodified);
}

if ($is304) {
	if (isset($_SERVER["SERVER_PROTOCOL"]) && $_SERVER["SERVER_PROTOCOL"] == "HTTP/1.1") 
		header("HTTP/1.1 304 Not Modified");
	else
		header("HTTP/1.0 304 Not Modified");
	header("Connection: close");
	exit;
}

header("Content-Type: $mime;charset=$charset");
if ($mime === "application/xhtml+xml") {
	print '<?xml version="1.0" encoding="' . $charset . '" ?>' . "\n";
}
if (DOCTYPE === "strict") { ?>
<!DOCTYPE html 
     PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<?php } else if (DOCTYPE === "html-strict") { ?>
<!DOCTYPE HTML 
     PUBLIC "-//W3C//DTD HTML 4.01//EN"
     "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<?php } else if (DOCTYPE === "math") { ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1 plus MathML 2.0//EN"
               "http://www.w3.org/TR/MathML2/dtd/xhtml-math11-f.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<?php } else { ?>
<!DOCTYPE html
   PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<?php } ?>
<head>
<?php if (DOCTYPE !== "html-strict") { ?>
<meta http-equiv="Content-Type" content="<?php echo $mime ?>;charset=<?php echo $charset ?>" />
<?php } else { ?>
<meta http-equiv="Content-Type" content="<?php echo $mime ?>;charset=<?php echo $charset ?>">
<?php } ?>