<?php
/*
	PHP script handling HTTP redirections. To be used as a custom HTTP 404 error page.

	Version 1.1, 2008-01-27, http://alexandre.alapetite.net/doc-alex/redirection-404/

	------------------------------------------------------------------
	Written by Alexandre Alapetite, http://alexandre.alapetite.net/cv/

	Open Source, Copyright 2007-2008
	Licence: Creative Commons "Attribution-ShareAlike 2.0 France", BY-SA (FR),
	http://creativecommons.org/licenses/by-sa/2.0/fr/
	- Attribution. You must give the original author credit
	- Share Alike. If you alter, transform, or build upon this work,
	  you may distribute the resulting work only under a license identical to this one
	  (Can be included in GPL/LGPL projects)
	- The French law is authoritative
	- Any of these conditions can be waived if you get permission from Alexandre Alapetite
	- Please send to Alexandre Alapetite the modifications you make,
	  in order to improve this file for the benefit of everybody

	If you want to distribute this code, please do it as a link to:
	http://alexandre.alapetite.net/doc-alex/redirection-404/
*/

//Constants
$path=(empty($_SERVER['SCRIPT_FILENAME']) ? '' : dirname($_SERVER['SCRIPT_FILENAME'])).'/404/'; //Root of the redirection structure (404.txt files)
$customRedirect='/'; //To specify an optional custom HTML redirection after the error message
$customRedirectTimeOut=5; //Time-out in second before redirection to the optional above address
$defaultNewServer=''; //Change the server of the new relative addresses: 'http://example.net:80'
$enableExternalServer=false; //Allow this server to receive errors from another server

//Get old address
$oldUrl='';
if ($enableExternalServer&&isset($_GET['REDIRECT_URL'])) $oldUrl=substr($_GET['REDIRECT_URL'],0,1024); //Redirected from another server
elseif (!empty($_SERVER['REQUEST_URI'])) $oldUrl=substr($_SERVER['REQUEST_URI'],0,1024); //Apache, IIS6
elseif (!empty($_SERVER['QUERY_STRING'])) $oldUrl=substr($_SERVER['QUERY_STRING'],0,1024); //IIS5 (defined but empty under Apache)
else $oldUrl='/_unknown_'; //Do not use $_SERVER['REDIRECT_URL'] (see Apache PHP module)
if (($sc=strpos($oldUrl,';'))!==false) $oldUrl=trim(substr($oldUrl,++$sc)); //IIS
$oldUrlParsed=parse_url($oldUrl);
$oldPath=$oldUrlParsed['path'];

//Search the best 404.txt mapping file in the file-tree structure
$absolute='/';
$dirs=explode('/',$oldPath); //We do not do urldecode(), so special characters (e.g. space) of local folders must be %-encoded: ./404/Hello%20World/404.txt
foreach($dirs as $dir)
	if (strlen($dir)>0)
	{
		if (is_dir($path.$dir))
		{
			$path.=$dir.'/';
			$absolute.=$dir.'/';
		}
		else break;
	}
$path.='404.txt';

//Search in the 404.txt file for the first matching for $oldPath
$newPath='';
$httpStatus=302;
$found=false;
if (is_file($path)&&($handle=@fopen($path,'r')))
{
	while (!feof($handle))
	{
		$line=trim(fgets($handle,4096));
		if ((strlen($line)<3)||($line[0]=='#')) continue; //comment or invalid
		$map=preg_split('"\s+"',$line,4);
		if (count($map)<2) continue; //invalid
		$mapOld=$map[1];
		if ($mapOld[0]!='/') $mapOld=$absolute.$mapOld;
		if (@preg_match('"^'.$mapOld.'$"iD',$oldPath)&&
		 ((($status=$map[0])==='gone')||
		  ((count($map)>2)&&
		   (strlen($newPath=@preg_replace('"^'.$mapOld.'$"iD',$map[2],$oldPath))>0))))
		{
			$found=true;
			switch ($status)
			{
				case 'permanent': $httpStatus=301; break;
				case 'found':
				case 'temp': $httpStatus=302; break;
				case 'seeother': $httpStatus=303; break;
				case 'temporary': $httpStatus=307; break;
				case 'gone': $httpStatus=410; break;
				default: $found=false;
			}
			if ($found&&(strlen($newPath)>0))
			{
				if (!preg_match('"^(?:(?:[a-z]{3,6}:)|(?:\.\./))"i',$newPath)) //No URI Scheme, and no ../ in front
				{//When it is possible and not already the case, make the redirection an absolute URL
					if (empty($defaultNewServer)&&isset($_SERVER['HTTP_HOST']))
					{
						$defaultNewServer='http://'.$_SERVER['HTTP_HOST'];
						if (isset($_SERVER['SERVER_PORT'])&&($_SERVER['SERVER_PORT']!='80'))
							$defaultNewServer.=':'.$_SERVER['SERVER_PORT'];
						if ($newPath[0]!=='/') //relative address
							$newPath=rtrim(substr($oldPath,-1,1)==='/' ? $oldPath : dirname($oldPath),'/\\').'/'.$newPath;
					}
					$newPath=$defaultNewServer.$newPath;
				}
				break;
			}
		}
	}
	fclose($handle);
}

if ($found) //Redirect if new address is found
{
	if ($httpStatus===410)
	{
		header('HTTP/1.1 410 Gone');
		header('Status: 410 Gone');
		echo '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" ',
		 '"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">'."\n",
		 '<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-GB" lang="en-GB">'."\n",
		 '<head>'."\n",
		 '<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />'."\n",
		 '<meta http-equiv="Content-Language" content="en-GB" />'."\n",
		 empty($customRedirect) ? '' : '<meta http-equiv="Refresh" content="'.$customRedirectTimeOut.'; url='.$customRedirect.'" />'."\n",
		 '<title>410 Gone</title>'."\n",
		 '<meta name="language" content="en-GB" />'."\n",
		 '<meta name="robots" content="noindex,follow" />'."\n",
		 '</head>'."\n",
		 '<body>'."\n",
		 '<h1>Gone</h1>'."\n",
		 '<p>The requested resource <kbd>'.$oldPath.'</kbd> is no longer available on this server and there is no forwarding address. ',
		 'Please remove all references to this resource.</p>'."\n",
		 '</body>'."\n",
		 '</html>'."\n";
	}
	else
	{
		if (isset($oldUrlParsed['query'])) $newPath.='?'.$oldUrlParsed['query'];
		$status=array(301=>'Moved Permanently',302=>'Found',303=>'See Other',307=>'Temporary Redirect');
		header('Location: '.$newPath);
		header('HTTP/1.1 '.$httpStatus.' '.$status[$httpStatus]);
		header('Status: '.$httpStatus.' '.$status[$httpStatus]);
		echo '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" ',
		 '"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">'."\n",
		 '<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-GB" lang="en-GB">'."\n",
		 '<head>'."\n",
		 '<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />'."\n",
		 '<meta http-equiv="Content-Language" content="en-GB" />'."\n",
		 '<meta http-equiv="Refresh" content="0; url='.$newPath.'" />'."\n",
		 '<title>'.$httpStatus.' '.$status[$httpStatus].'</title>'."\n",
		 '<meta name="language" content="en-GB" />'."\n",
		 '<meta name="robots" content="noindex,follow" />'."\n",
		 '</head>'."\n",
		 '<body>'."\n",
		 '<h1>'.$status[$httpStatus].'</h1>'."\n",
		 '<p>The document has moved <a href="'.$newPath.'">here</a>.</p>'."\n",
		 '</body>'."\n",
		 '</html>'."\n";
	}
}
else //404 error message
{
	header('HTTP/1.1 404 Not Found');
	header('Status: 404 Not Found');
	echo '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" ',
	 '"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">'."\n",
	 '<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-GB" lang="en-GB">'."\n",
	 '<head>'."\n",
	 '<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />'."\n",
	 '<meta http-equiv="Content-Language" content="en-GB" />'."\n",
	 empty($customRedirect) ? '' : '<meta http-equiv="Refresh" content="'.$customRedirectTimeOut.'; url='.$customRedirect.'" />'."\n",
	 '<title>404 Not Found</title>'."\n",
	 '<meta name="language" content="en-GB" />'."\n",
	 '<meta name="robots" content="noindex,follow" />'."\n",
	 '</head>'."\n",
	 '<body>'."\n",
	 '<h1>Not Found</h1>'."\n",
	 '<p>The requested <abbr title="Uniform Resource Locator">URL</abbr> <kbd>'.$oldPath.'</kbd> was not found on this server.</p>'."\n",
	 '</body>'."\n",
	 '</html>'."\n";
}
?>