function session_pagestart($user_ip, $thispage_id)
{
	global $db, $lang, $board_config;
	global $HTTP_COOKIE_VARS, $HTTP_GET_VARS, $SID;

	$cookiename = $board_config['cookie_name'];
	$cookiepath = $board_config['cookie_path'];
	$cookiedomain = $board_config['cookie_domain'];
	$cookiesecure = $board_config['cookie_secure'];

	$current_time = time();
	unset($userdata);

	if ( isset($HTTP_COOKIE_VARS[$cookiename . '_sid']) || isset($HTTP_COOKIE_VARS[$cookiename . '_data']) )
	{
		$sessiondata = isset( $HTTP_COOKIE_VARS[$cookiename . '_data'] ) ? unserialize(stripslashes($HTTP_COOKIE_VARS[$cookiename . '_data'])) : array();
		$session_id = isset( $HTTP_COOKIE_VARS[$cookiename . '_sid'] ) ? $HTTP_COOKIE_VARS[$cookiename . '_sid'] : '';
		$sessionmethod = SESSION_METHOD_COOKIE;
	}
	else
	{
		$sessiondata = array();
		$session_id = ( isset($HTTP_GET_VARS['sid']) ) ? $HTTP_GET_VARS['sid'] : '';
		$sessionmethod = SESSION_METHOD_GET;
	}

	// 
	if (!preg_match('/^[A-Za-z0-9]*$/', $session_id))
	{
		$session_id = '';
	}

	$thispage_id = (int) $thispage_id;

	//
	// Does a session exist?
	//
	if ( !empty($session_id) )
	{
		//
		// session_id exists so go ahead and attempt to grab all
		// data in preparation
		//
		$sql = "SELECT u.*, s.*
			FROM " . SESSIONS_TABLE . " s, " . USERS_TABLE . " u
			WHERE s.session_id = '$session_id'
				AND u.user_id = s.session_user_id";
		if ( !($result = $db->sql_query($sql)) )
		{
			message_die(CRITICAL_ERROR, 'Error doing DB query userdata row fetch', '', __LINE__, __FILE__, $sql);
		}

		$userdata = $db->sql_fetchrow($result);

		//
		// Did the session exist in the DB?
		//
		if ( isset($userdata['user_id']) )
		{
			//
			// Do not check IP assuming equivalence, if IPv4 we'll check only first 24
			// bits ... I've been told (by vHiker) this should alleviate problems with 
			// load balanced et al proxies while retaining some reliance on IP security.
			//
			$ip_check_s = substr($userdata['session_ip'], 0, 6);
			$ip_check_u = substr($user_ip, 0, 6);

			if ($ip_check_s == $ip_check_u)
			{
				$SID = ($sessionmethod == SESSION_METHOD_GET || defined('IN_ADMIN')) ? 'sid=' . $session_id : '';

				//
				// Only update session DB a minute or so after last update
				//
				if ( $current_time - $userdata['session_time'] > 60 )
				{
					// A little trick to reset session_admin on session re-usage
					$update_admin = (!defined('IN_ADMIN') && $current_time - $userdata['session_time'] > ($board_config['session_length']+60)) ? ', session_admin = 0' : '';

					$sql = "UPDATE " . SESSIONS_TABLE . " 
						SET session_time = $current_time, session_page = $thispage_id$update_admin
						WHERE session_id = '" . $userdata['session_id'] . "'";
					if ( !$db->sql_query($sql) )
					{
						message_die(CRITICAL_ERROR, 'Error updating sessions table', '', __LINE__, __FILE__, $sql);
					}

					if ( $userdata['user_id'] != ANONYMOUS )
					{
						$sql = "UPDATE " . USERS_TABLE . " 
							SET user_session_time = $current_time, user_session_page = $thispage_id
							WHERE user_id = " . $userdata['user_id'];
						if ( !$db->sql_query($sql) )
						{
							message_die(CRITICAL_ERROR, 'Error updating sessions table', '', __LINE__, __FILE__, $sql);
						}
					}

					session_clean($userdata['session_id']);

					setcookie($cookiename . '_data', serialize($sessiondata), $current_time + 31536000, $cookiepath, $cookiedomain, $cookiesecure);
					setcookie($cookiename . '_sid', $session_id, 0, $cookiepath, $cookiedomain, $cookiesecure);
				}

				return $userdata;
			}
		}
	}

	//
	// If we reach here then no (valid) session exists. So we'll create a new one,
	// using the cookie user_id if available to pull basic user prefs.
	//
	$user_id = ( isset($sessiondata['userid']) ) ? intval($sessiondata['userid']) : ANONYMOUS;

	if ( !($userdata = session_begin($user_id, $user_ip, $thispage_id, TRUE)) )
	{
		message_die(CRITICAL_ERROR, 'Error creating user session', '', __LINE__, __FILE__, $sql);
	}

	return $userdata;

}