SimpleMachines / SMF2.1

Sources/QueryString.php

<?php

/**
 * This file does a lot of important stuff.  Mainly, this means it handles
 * the query string, request variables, and session management.
 *
 * Simple Machines Forum (SMF)
 *
 * @package SMF
 * @author Simple Machines https://www.simplemachines.org
 * @copyright 2022 Simple Machines and individual contributors
 * @license https://www.simplemachines.org/about/smf/license.php BSD
 *
 * @version 2.1.0
 */

if (!defined('SMF'))
	die('No direct access...');

/**
 * Clean the request variables - add html entities to GET and slashes if magic_quotes_gpc is Off.
 *
 * What it does:
 * - cleans the request variables (ENV, GET, POST, COOKIE, SERVER) and
 * - makes sure the query string was parsed correctly.
 * - handles the URLs passed by the queryless URLs option.
 * - makes sure, regardless of php.ini, everything has slashes.
 * - sets up $board, $topic, and $scripturl and $_REQUEST['start'].
 * - determines, or rather tries to determine, the client's IP.
 */

function cleanRequest()
{
	global $board, $topic, $boardurl, $scripturl, $modSettings, $smcFunc;

	// Makes it easier to refer to things this way.
	$scripturl = $boardurl . '/index.php';

	// What function to use to reverse magic quotes - if sybase is on we assume that the database sensibly has the right unescape function!
	$removeMagicQuoteFunction = ini_get('magic_quotes_sybase') || strtolower(ini_get('magic_quotes_sybase')) == 'on' ? 'unescapestring__recursive' : 'stripslashes__recursive';
	$magicQuotesEnabled = version_compare(PHP_VERSION, '7.4.0') == -1 && function_exists('get_magic_quotes_gpc') && @get_magic_quotes_gpc() != 0 && empty($modSettings['integrate_magic_quotes']);

	// Save some memory.. (since we don't use these anyway.)
	unset($GLOBALS['HTTP_POST_VARS'], $GLOBALS['HTTP_POST_VARS']);
	unset($GLOBALS['HTTP_POST_FILES'], $GLOBALS['HTTP_POST_FILES']);

	// These keys shouldn't be set...ever.
	if (isset($_REQUEST['GLOBALS']) || isset($_COOKIE['GLOBALS']))
		die('Invalid request variable.');

Using exit here is not recommended.

	// Same goes for numeric keys.
	foreach (array_merge(array_keys($_POST), array_keys($_GET), array_keys($_FILES)) as $key)
		if (is_numeric($key))
			die('Numeric request keys are invalid.');

Using exit here is not recommended.

	// Numeric keys in cookies are less of a problem. Just unset those.
	foreach ($_COOKIE as $key => $value)
		if (is_numeric($key))
			unset($_COOKIE[$key]);

	// Get the correct query string.  It may be in an environment variable...
	if (!isset($_SERVER['QUERY_STRING']))
		$_SERVER['QUERY_STRING'] = getenv('QUERY_STRING');

	// It seems that sticking a URL after the query string is mighty common, well, it's evil - don't.
	if (strpos($_SERVER['QUERY_STRING'], 'http') === 0)
	{
		send_http_status(400);
		die;

Using exit here is not recommended.

	}

	// Are we going to need to parse the ; out?
	if (strpos(ini_get('arg_separator.input'), ';') === false && !empty($_SERVER['QUERY_STRING']))
	{
		// Get rid of the old one! You don't know where it's been!
		$_GET = array();

		// Was this redirected? If so, get the REDIRECT_QUERY_STRING.
		// Do not urldecode() the querystring.
		$_SERVER['QUERY_STRING'] = substr($_SERVER['QUERY_STRING'], 0, 5) === 'url=/' ? $_SERVER['REDIRECT_QUERY_STRING'] : $_SERVER['QUERY_STRING'];

		// Replace ';' with '&' and '&something&' with '&something=&'.  (this is done for compatibility...)
		// @todo smflib
		parse_str(preg_replace('/&(\w+)(?=&|$)/', '&$1=', strtr($_SERVER['QUERY_STRING'], array(';?' => '&', ';' => '&', '%00' => '', "\0" => ''))), $_GET);

		// Magic quotes still applies with parse_str - so clean it up.
		if ($magicQuotesEnabled)
			$_GET = $removeMagicQuoteFunction($_GET);
	}
	elseif (strpos(ini_get('arg_separator.input'), ';') !== false)
	{
		if ($magicQuotesEnabled)
			$_GET = $removeMagicQuoteFunction($_GET);

		// Search engines will send action=profile%3Bu=1, which confuses PHP.
		foreach ($_GET as $k => $v)
		{
			if ((string) $v === $v && strpos($k, ';') !== false)
			{
				$temp = explode(';', $v);
				$_GET[$k] = $temp[0];

				for ($i = 1, $n = count($temp); $i < $n; $i++)
				{
					@list ($key, $val) = @explode('=', $temp[$i], 2);
					if (!isset($_GET[$key]))
						$_GET[$key] = $val;
				}
			}

			// This helps a lot with integration!
			if (strpos($k, '?') === 0)
			{
				$_GET[substr($k, 1)] = $v;
				unset($_GET[$k]);
			}
		}
	}

	// There's no query string, but there is a URL... try to get the data from there.
	if (!empty($_SERVER['REQUEST_URI']))
	{
		// Remove the .html, assuming there is one.
		if (substr($_SERVER['REQUEST_URI'], strrpos($_SERVER['REQUEST_URI'], '.'), 4) == '.htm')
			$request = substr($_SERVER['REQUEST_URI'], 0, strrpos($_SERVER['REQUEST_URI'], '.'));
		else
			$request = $_SERVER['REQUEST_URI'];

		// @todo smflib.
		// Replace 'index.php/a,b,c/d/e,f' with 'a=b,c&d=&e=f' and parse it into $_GET.
		if (strpos($request, basename($scripturl) . '/') !== false)
		{
			parse_str(substr(preg_replace('/&(\w+)(?=&|$)/', '&$1=', strtr(preg_replace('~/([^,/]+),~', '/$1=', substr($request, strpos($request, basename($scripturl)) + strlen(basename($scripturl)))), '/', '&')), 1), $temp);
			if (function_exists('get_magic_quotes_gpc') && @get_magic_quotes_gpc() != 0 && empty($modSettings['integrate_magic_quotes']))
				$temp = $removeMagicQuoteFunction($temp);
			$_GET += $temp;
		}
	}

	// If magic quotes is on we have some work...
	if ($magicQuotesEnabled)
	{
		$_ENV = $removeMagicQuoteFunction($_ENV);
		$_POST = $removeMagicQuoteFunction($_POST);
		$_COOKIE = $removeMagicQuoteFunction($_COOKIE);
		foreach ($_FILES as $k => $dummy)
			if (isset($_FILES[$k]['name']))
				$_FILES[$k]['name'] = $removeMagicQuoteFunction($_FILES[$k]['name']);
	}

	// Add entities to GET.  This is kinda like the slashes on everything else.
	$_GET = htmlspecialchars__recursive($_GET);

	// Let's not depend on the ini settings... why even have COOKIE in there, anyway?
	$_REQUEST = $_POST + $_GET;

	// Make sure $board and $topic are numbers.
	if (isset($_REQUEST['board']))
	{
		// Make sure its a string and not something else like an array
		$_REQUEST['board'] = (string) $_REQUEST['board'];

		// If there's a slash in it, we've got a start value! (old, compatible links.)
		if (strpos($_REQUEST['board'], '/') !== false)
			list ($_REQUEST['board'], $_REQUEST['start']) = explode('/', $_REQUEST['board']);
		// Same idea, but dots.  This is the currently used format - ?board=1.0...
		elseif (strpos($_REQUEST['board'], '.') !== false)
			list ($_REQUEST['board'], $_REQUEST['start']) = explode('.', $_REQUEST['board']);
		// Now make absolutely sure it's a number.
		$board = (int) $_REQUEST['board'];
		$_REQUEST['start'] = isset($_REQUEST['start']) ? (int) $_REQUEST['start'] : 0;

		// This is for "Who's Online" because it might come via POST - and it should be an int here.
		$_GET['board'] = $board;
	}
	// Well, $board is going to be a number no matter what.
	else
		$board = 0;

	// If there's a threadid, it's probably an old YaBB SE link.  Flow with it.
	if (isset($_REQUEST['threadid']) && !isset($_REQUEST['topic']))
		$_REQUEST['topic'] = $_REQUEST['threadid'];

	// We've got topic!
	if (isset($_REQUEST['topic']))
	{
		// Make sure its a string and not something else like an array
		$_REQUEST['topic'] = (string) $_REQUEST['topic'];

		// Slash means old, beta style, formatting.  That's okay though, the link should still work.
		if (strpos($_REQUEST['topic'], '/') !== false)
			list ($_REQUEST['topic'], $_REQUEST['start']) = explode('/', $_REQUEST['topic']);
		// Dots are useful and fun ;).  This is ?topic=1.15.
		elseif (strpos($_REQUEST['topic'], '.') !== false)
			list ($_REQUEST['topic'], $_REQUEST['start']) = explode('.', $_REQUEST['topic']);

		// Topic should always be an integer
		$topic = $_GET['topic'] = $_REQUEST['topic'] = (int) $_REQUEST['topic'];

		// Start could be a lot of things...
		// ... empty ...
		if (empty($_REQUEST['start']))
		{
			$_REQUEST['start'] = 0;
		}
		// ... a simple number ...
		elseif (is_numeric($_REQUEST['start']))
		{
			$_REQUEST['start'] = (int) $_REQUEST['start'];
		}
		// ... or a specific message ...
		elseif (strpos($_REQUEST['start'], 'msg') === 0)
		{
			$virtual_msg = (int) substr($_REQUEST['start'], 3);
			$_REQUEST['start'] = $virtual_msg === 0 ? 0 : 'msg' . $virtual_msg;
		}
		// ... or whatever is new ...
		elseif (strpos($_REQUEST['start'], 'new') === 0)
		{
			$_REQUEST['start'] = 'new';
		}
		// ... or since a certain time ...
		elseif (strpos($_REQUEST['start'], 'from') === 0)
		{
			$timestamp = (int) substr($_REQUEST['start'], 4);
			$_REQUEST['start'] = $timestamp === 0 ? 0 : 'from' . $timestamp;
		}
		// ... or something invalid, in which case we reset it to 0.
		else
			$_REQUEST['start'] = 0;
	}
	else
		$topic = 0;

	// There should be a $_REQUEST['start'], some at least.  If you need to default to other than 0, use $_GET['start'].
	if (empty($_REQUEST['start']) || $_REQUEST['start'] < 0 || (int) $_REQUEST['start'] > 2147473647)
		$_REQUEST['start'] = 0;

	// The action needs to be a string and not an array or anything else
	if (isset($_REQUEST['action']))
		$_REQUEST['action'] = (string) $_REQUEST['action'];
	if (isset($_GET['action']))
		$_GET['action'] = (string) $_GET['action'];

	// Some mail providers like to encode semicolons in activation URLs...
	if (!empty($_REQUEST['action']) && substr($_SERVER['QUERY_STRING'], 0, 18) == 'action=activate%3b')
	{
		header('location: ' . $scripturl . '?' . str_replace('%3b', ';', $_SERVER['QUERY_STRING']));
		exit;
	}

	// Make sure we have a valid REMOTE_ADDR.
	if (!isset($_SERVER['REMOTE_ADDR']))
	{
		$_SERVER['REMOTE_ADDR'] = '';
		// A new magic variable to indicate we think this is command line.
		$_SERVER['is_cli'] = true;
	}
	// Perhaps we have a IPv6 address.
	elseif (isValidIP($_SERVER['REMOTE_ADDR']))
	{
		$_SERVER['REMOTE_ADDR'] = preg_replace('~^::ffff:(\d+\.\d+\.\d+\.\d+)~', '\1', $_SERVER['REMOTE_ADDR']);
	}

	// Try to calculate their most likely IP for those people behind proxies (And the like).
	$_SERVER['BAN_CHECK_IP'] = $_SERVER['REMOTE_ADDR'];

	// If we haven't specified how to handle Reverse Proxy IP headers, lets do what we always used to do.
	if (!isset($modSettings['proxy_ip_header']))
		$modSettings['proxy_ip_header'] = 'autodetect';

	// Which headers are we going to check for Reverse Proxy IP headers?
	if ($modSettings['proxy_ip_header'] == 'disabled')
		$reverseIPheaders = array();
	elseif ($modSettings['proxy_ip_header'] == 'autodetect')
		$reverseIPheaders = array('HTTP_X_FORWARDED_FOR', 'HTTP_CLIENT_IP', 'HTTP_X_REAL_IP', 'HTTP_CF_CONNECTING_IP');
	else
		$reverseIPheaders = array($modSettings['proxy_ip_header']);

	// Find the user's IP address. (but don't let it give you 'unknown'!)
	foreach ($reverseIPheaders as $proxyIPheader)
	{
		// Ignore if this is not set.
		if (!isset($_SERVER[$proxyIPheader]))
			continue;

		if (!empty($modSettings['proxy_ip_servers']))
		{
			$valid_sender = false;

			foreach (explode(',', $modSettings['proxy_ip_servers']) as $proxy)
			{
				if ($proxy == $_SERVER['REMOTE_ADDR'] || matchIPtoCIDR($_SERVER['REMOTE_ADDR'], $proxy))
				{
					$valid_sender = true;
					break;
				}
			}

			if (!$valid_sender)
				continue;
		}

		// If there are commas, get the last one.. probably.
		if (strpos($_SERVER[$proxyIPheader], ',') !== false)
		{
			$ips = array_reverse(explode(', ', $_SERVER[$proxyIPheader]));

			// Go through each IP...
			foreach ($ips as $i => $ip)
			{
				// Make sure it's in a valid range...
				if (preg_match('~^((0|10|172\.(1[6-9]|2[0-9]|3[01])|192\.168|255|127)\.|unknown|::1|fe80::|fc00::)~', $ip) != 0 && preg_match('~^((0|10|172\.(1[6-9]|2[0-9]|3[01])|192\.168|255|127)\.|unknown|::1|fe80::|fc00::)~', $_SERVER['REMOTE_ADDR']) == 0)
				{
					if (!isValidIPv6($_SERVER[$proxyIPheader]) || preg_match('~::ffff:\d+\.\d+\.\d+\.\d+~', $_SERVER[$proxyIPheader]) !== 0)
					{
						$_SERVER[$proxyIPheader] = preg_replace('~^::ffff:(\d+\.\d+\.\d+\.\d+)~', '\1', $_SERVER[$proxyIPheader]);

						// Just incase we have a legacy IPv4 address.
						// @ TODO: Convert to IPv6.
						if (preg_match('~^((([1]?\d)?\d|2[0-4]\d|25[0-5])\.){3}(([1]?\d)?\d|2[0-4]\d|25[0-5])$~', $_SERVER[$proxyIPheader]) === 0)
							continue;
					}

					continue;
				}

				// Otherwise, we've got an IP!
				$_SERVER['BAN_CHECK_IP'] = trim($ip);
				break;
			}
		}
		// Otherwise just use the only one.
		elseif (preg_match('~^((0|10|172\.(1[6-9]|2[0-9]|3[01])|192\.168|255|127)\.|unknown|::1|fe80::|fc00::)~', $_SERVER[$proxyIPheader]) == 0 || preg_match('~^((0|10|172\.(1[6-9]|2[0-9]|3[01])|192\.168|255|127)\.|unknown|::1|fe80::|fc00::)~', $_SERVER['REMOTE_ADDR']) != 0)
			$_SERVER['BAN_CHECK_IP'] = $_SERVER[$proxyIPheader];
		elseif (!isValidIPv6($_SERVER[$proxyIPheader]) || preg_match('~::ffff:\d+\.\d+\.\d+\.\d+~', $_SERVER[$proxyIPheader]) !== 0)
		{
			$_SERVER[$proxyIPheader] = preg_replace('~^::ffff:(\d+\.\d+\.\d+\.\d+)~', '\1', $_SERVER[$proxyIPheader]);

			// Just incase we have a legacy IPv4 address.
			// @ TODO: Convert to IPv6.
			if (preg_match('~^((([1]?\d)?\d|2[0-4]\d|25[0-5])\.){3}(([1]?\d)?\d|2[0-4]\d|25[0-5])$~', $_SERVER[$proxyIPheader]) === 0)
				continue;
		}
	}

	// Make sure we know the URL of the current request.
	if (empty($_SERVER['REQUEST_URI']))
		$_SERVER['REQUEST_URL'] = $scripturl . (!empty($_SERVER['QUERY_STRING']) ? '?' . $_SERVER['QUERY_STRING'] : '');
	elseif (preg_match('~^([^/]+//[^/]+)~', $scripturl, $match) == 1)
		$_SERVER['REQUEST_URL'] = $match[1] . $_SERVER['REQUEST_URI'];
	else
		$_SERVER['REQUEST_URL'] = $_SERVER['REQUEST_URI'];

	// And make sure HTTP_USER_AGENT is set.
	$_SERVER['HTTP_USER_AGENT'] = isset($_SERVER['HTTP_USER_AGENT']) ? (isset($smcFunc['htmlspecialchars']) ? $smcFunc['htmlspecialchars']($smcFunc['db_unescape_string']($_SERVER['HTTP_USER_AGENT']), ENT_QUOTES) : htmlspecialchars($smcFunc['db_unescape_string']($_SERVER['HTTP_USER_AGENT']), ENT_QUOTES)) : '';

	// Some final checking.
	if (!isValidIP($_SERVER['BAN_CHECK_IP']))
		$_SERVER['BAN_CHECK_IP'] = '';
	if ($_SERVER['REMOTE_ADDR'] == 'unknown')
		$_SERVER['REMOTE_ADDR'] = '';
}

/**
 * Validates a IPv6 address. returns true if it is ipv6.
 *
 * @param string $ip The ip address to be validated
 * @return boolean Whether the specified IP is a valid IPv6 address
 */
function isValidIPv6($ip)
{
	//looking for :
	if (strpos($ip, ':') === false)
		return false;

	//check valid address
	return filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6);
}

/**
 * Expands a IPv6 address to its full form.
 *
 * @param string $addr The IPv6 address
 * @param bool $strict_check Whether to check the length of the expanded address for compliance
 * @return string|bool The expanded IPv6 address or false if $strict_check is true and the result isn't valid
 */
function expandIPv6($addr, $strict_check = true)
{
	static $converted = array();

	// Check if we have done this already.
	if (isset($converted[$addr]))
		return $converted[$addr];

	// Check if there are segments missing, insert if necessary.
	if (strpos($addr, '::') !== false)
	{
		$part = explode('::', $addr);
		$part[0] = explode(':', $part[0]);
		$part[1] = explode(':', $part[1]);
		$missing = array();

		for ($i = 0; $i < (8 - (count($part[0]) + count($part[1]))); $i++)
			array_push($missing, '0000');

		$part = array_merge($part[0], $missing, $part[1]);
	}
	else
		$part = explode(':', $addr);

	// Pad each segment until it has 4 digits.
	foreach ($part as &$p)
		while (strlen($p) < 4)
			$p = '0' . $p;

	unset($p);

	// Join segments.
	$result = implode(':', $part);

	// Save this incase of repeated use.
	$converted[$addr] = $result;

	// Quick check to make sure the length is as expected.
	if (!$strict_check || strlen($result) == 39)
		return $result;
	else
		return false;
}

/**
 * Detect if a IP is in a CIDR address
 * - returns true or false
 *
 * @param string $ip_address IP address to check
 * @param string $cidr_address CIDR address to verify
 * @return bool Whether the IP matches the CIDR
 */
function matchIPtoCIDR($ip_address, $cidr_address)
{
	list ($cidr_network, $cidr_subnetmask) = preg_split('/', $cidr_address);

	//v6?
	if ((strpos($cidr_network, ':') !== false))
	{
		if (!filter_var($ip_address, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6) || !filter_var($cidr_network, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6))
			return false;

		$ip_address = inet_pton($ip_address);
		$cidr_network = inet_pton($cidr_network);
		$binMask = str_repeat("f", $cidr_subnetmask / 4);
		switch ($cidr_subnetmask % 4)
		{
			case 0:
				break;
			case 1:
				$binMask .= "8";
				break;
			case 2:
				$binMask .= "c";
				break;
			case 3:
				$binMask .= "e";
				break;
		}
		$binMask = str_pad($binMask, 32, '0');
		$binMask = pack("H*", $binMask);

		return ($ip_address & $binMask) == $cidr_network;

Are you sure you want to use the bitwise & or did you mean &&?

	}
	else
		return (ip2long($ip_address) & (~((1 << (32 - $cidr_subnetmask)) - 1))) == ip2long($cidr_network);
}

/**
 * Adds slashes to the array/variable.
 * What it does:
 * - returns the var, as an array or string, with escapes as required.
 * - importantly escapes all keys and values!
 * - calls itself recursively if necessary.
 *
 * @param array|string $var A string or array of strings to escape
 * @return array|string The escaped string or array of escaped strings
 */
function escapestring__recursive($var)
{
	global $smcFunc;

	if (!is_array($var))
		return $smcFunc['db_escape_string']($var);

	// Reindex the array with slashes.
	$new_var = array();

	// Add slashes to every element, even the indexes!
	foreach ($var as $k => $v)
		$new_var[$smcFunc['db_escape_string']($k)] = escapestring__recursive($v);

	return $new_var;
}

/**
 * Adds html entities to the array/variable.  Uses two underscores to guard against overloading.
 * What it does:
 * - adds entities (&quot;, &lt;, &gt;) to the array or string var.
 * - importantly, does not effect keys, only values.
 * - calls itself recursively if necessary.
 *
 * @param array|string $var The string or array of strings to add entites to
 * @param int $level Which level we're at within the array (if called recursively)
 * @return array|string The string or array of strings with entities added
 */
function htmlspecialchars__recursive($var, $level = 0)
{
	global $smcFunc;

	if (!is_array($var))
		return isset($smcFunc['htmlspecialchars']) ? $smcFunc['htmlspecialchars']($var, ENT_QUOTES) : htmlspecialchars($var, ENT_QUOTES);

	// Add the htmlspecialchars to every element.
	foreach ($var as $k => $v)
		$var[$k] = $level > 25 ? null : htmlspecialchars__recursive($v, $level + 1);

	return $var;
}

/**
 * Removes url stuff from the array/variable.  Uses two underscores to guard against overloading.
 * What it does:
 * - takes off url encoding (%20, etc.) from the array or string var.
 * - importantly, does it to keys too!
 * - calls itself recursively if there are any sub arrays.
 *
 * @param array|string $var The string or array of strings to decode
 * @param int $level Which level we're at within the array (if called recursively)
 * @return array|string The decoded string or array of decoded strings
 */
function urldecode__recursive($var, $level = 0)
{
	if (!is_array($var))
		return urldecode($var);

	// Reindex the array...
	$new_var = array();

	// Add the htmlspecialchars to every element.
	foreach ($var as $k => $v)
		$new_var[urldecode($k)] = $level > 25 ? null : urldecode__recursive($v, $level + 1);

	return $new_var;
}

/**
 * Unescapes any array or variable.  Uses two underscores to guard against overloading.
 * What it does:
 * - unescapes, recursively, from the array or string var.
 * - effects both keys and values of arrays.
 * - calls itself recursively to handle arrays of arrays.
 *
 * @param array|string $var The string or array of strings to unescape
 * @return array|string The unescaped string or array of unescaped strings
 */
function unescapestring__recursive($var)
{
	global $smcFunc;

	if (!is_array($var))
		return $smcFunc['db_unescape_string']($var);

	// Reindex the array without slashes, this time.
	$new_var = array();

	// Strip the slashes from every element.
	foreach ($var as $k => $v)
		$new_var[$smcFunc['db_unescape_string']($k)] = unescapestring__recursive($v);

	return $new_var;
}

/**
 * Remove slashes recursively.  Uses two underscores to guard against overloading.
 * What it does:
 * - removes slashes, recursively, from the array or string var.
 * - effects both keys and values of arrays.
 * - calls itself recursively to handle arrays of arrays.
 *
 * @param array|string $var The string or array of strings to strip slashes from
 * @param int $level = 0 What level we're at within the array (if called recursively)
 * @return array|string The string or array of strings with slashes stripped
 */
function stripslashes__recursive($var, $level = 0)
{
	if (!is_array($var))
		return stripslashes($var);

	// Reindex the array without slashes, this time.
	$new_var = array();

	// Strip the slashes from every element.
	foreach ($var as $k => $v)
		$new_var[stripslashes($k)] = $level > 25 ? null : stripslashes__recursive($v, $level + 1);

	return $new_var;
}

/**
 * Trim a string including the HTML space, character 160.  Uses two underscores to guard against overloading.
 * What it does:
 * - trims a string or an the var array using html characters as well.
 * - does not effect keys, only values.
 * - may call itself recursively if needed.
 *
 * @param array|string $var The string or array of strings to trim
 * @param int $level = 0 How deep we're at within the array (if called recursively)
 * @return array|string The trimmed string or array of trimmed strings
 */
function htmltrim__recursive($var, $level = 0)
{
	global $smcFunc;

	// Remove spaces (32), tabs (9), returns (13, 10, and 11), nulls (0), and hard spaces. (160)
	if (!is_array($var))
		return isset($smcFunc) ? $smcFunc['htmltrim']($var) : trim($var, ' ' . "\t\n\r\x0B" . '\0' . "\xA0");

	// Go through all the elements and remove the whitespace.
	foreach ($var as $k => $v)
		$var[$k] = $level > 25 ? null : htmltrim__recursive($v, $level + 1);

	return $var;
}

/**
 * Rewrite URLs to include the session ID.
 * What it does:
 * - rewrites the URLs outputted to have the session ID, if the user
 *   is not accepting cookies and is using a standard web browser.
 * - handles rewriting URLs for the queryless URLs option.
 * - can be turned off entirely by setting $scripturl to an empty
 *   string, ''. (it wouldn't work well like that anyway.)
 * - because of bugs in certain builds of PHP, does not function in
 *   versions lower than 4.3.0 - please upgrade if this hurts you.
 *
 * @param string $buffer The unmodified output buffer
 * @return string The modified buffer
 */
function ob_sessrewrite($buffer)
{
	global $scripturl, $modSettings, $context;

	// If $scripturl is set to nothing, or the SID is not defined (SSI?) just quit.
	if ($scripturl == '' || !defined('SID'))
		return $buffer;

	// Do nothing if the session is cookied, or they are a crawler - guests are caught by redirectexit().  This doesn't work below PHP 4.3.0, because it makes the output buffer bigger.
	// @todo smflib
	if (empty($_COOKIE) && SID != '' && !isBrowser('possibly_robot'))
		$buffer = preg_replace('/(?<!<link rel="canonical" href=)"' . preg_quote($scripturl, '/') . '(?!\?' . preg_quote(SID, '/') . ')\\??/', '"' . $scripturl . '?' . SID . '&amp;', $buffer);
	// Debugging templates, are we?
	elseif (isset($_GET['debug']))
		$buffer = preg_replace('/(?<!<link rel="canonical" href=)"' . preg_quote($scripturl, '/') . '\\??/', '"' . $scripturl . '?debug;', $buffer);

	// This should work even in 4.2.x, just not CGI without cgi.fix_pathinfo.
	if (!empty($modSettings['queryless_urls']) && (!$context['server']['is_cgi'] || ini_get('cgi.fix_pathinfo') == 1 || @get_cfg_var('cgi.fix_pathinfo') == 1) && ($context['server']['is_apache'] || $context['server']['is_lighttpd'] || $context['server']['is_litespeed']))
	{
		// Let's do something special for session ids!
		if (defined('SID') && SID != '')
			$buffer = preg_replace_callback(
				'~"' . preg_quote($scripturl, '~') . '\?(?:' . SID . '(?:;|&|&amp;))((?:board|topic)=[^#"]+?)(#[^"]*?)?"~',
				function($m)
				{
					global $scripturl;

					return '"' . $scripturl . "/" . strtr("$m[1]", '&;=', '//,') . ".html?" . SID . (isset($m[2]) ? $m[2] : "") . '"';
				},
				$buffer
			);
		else
			$buffer = preg_replace_callback(
				'~"' . preg_quote($scripturl, '~') . '\?((?:board|topic)=[^#"]+?)(#[^"]*?)?"~',
				function($m)
				{
					global $scripturl;

					return '"' . $scripturl . '/' . strtr("$m[1]", '&;=', '//,') . '.html' . (isset($m[2]) ? $m[2] : "") . '"';
				},
				$buffer
			);
	}

	// Return the changed buffer.
	return $buffer;
}

?>