diff --git a/phpBB/adm/index.php b/phpBB/adm/index.php
index c66935d84a..59ef826df4 100644
--- a/phpBB/adm/index.php
+++ b/phpBB/adm/index.php
@@ -30,11 +30,11 @@ phpbb::$user->setup('acp/common');
 // End session management
 
 // Have they authenticated (again) as an admin for this session?
-if (phpbb::$user->data['user_id'] != ANONYMOUS &&  (!isset(phpbb::$user->data['session_admin']) || !phpbb::$user->data['session_admin']))
+if (!phpbb::$user->is_guest && (!isset(phpbb::$user->data['session_admin']) || !phpbb::$user->data['session_admin']))
 {
 	login_box('', phpbb::$user->lang['LOGIN_ADMIN_CONFIRM'], phpbb::$user->lang['LOGIN_ADMIN_SUCCESS'], true, false);
 }
-else if (phpbb::$user->data['user_id'] == ANONYMOUS)
+else if (phpbb::$user->is_guest)
 {
 	login_box('');
 }
@@ -114,7 +114,7 @@ function adm_page_header($page_title)
 
 	phpbb::$template->assign_vars(array(
 		'PAGE_TITLE'			=> $page_title,
-		'USERNAME'				=> (phpbb::$user->data['user_id'] != ANONYMOUS) ? phpbb::$user->data['username'] : '',
+		'USERNAME'				=> (!phpbb::$user->is_guest) ? phpbb::$user->data['username'] : '',
 
 		'SESSION_ID'			=> phpbb::$user->session_id,
 		'ROOT_PATH'				=> PHPBB_ADMIN_PATH,
@@ -125,7 +125,7 @@ function adm_page_header($page_title)
 		'U_INDEX'				=> phpbb::$url->append_sid('index'),
 
 		'S_USER_ADMIN'			=> phpbb::$user->data['session_admin'],
-		'S_USER_LOGGED_IN'		=> (phpbb::$user->data['user_id'] != ANONYMOUS && !phpbb::$user->is_bot),
+		'S_USER_LOGGED_IN'		=> (phpbb::$user->is_registered),
 
 		'T_IMAGES_PATH'			=> PHPBB_ROOT_PATH . 'images/',
 		'T_SMILIES_PATH'		=> PHPBB_ROOT_PATH . phpbb::$config['smilies_path'] . '/',
diff --git a/phpBB/includes/functions.php b/phpBB/includes/functions.php
index 921c17e957..6ea76617fa 100644
--- a/phpBB/includes/functions.php
+++ b/phpBB/includes/functions.php
@@ -38,6 +38,14 @@ function request_var($var_name, $default, $multibyte = false, $cookie = false)
 	return phpbb_request::variable($var_name, $default, $multibyte, ($cookie) ? phpbb_request::COOKIE : phpbb_request::REQUEST);
 }
 
+/**
+* Wrapper for phpbb::$url->append_sid()
+*/
+function append_sid($url, $params = false, $is_amp = true, $session_id = false)
+{
+	return phpbb::$url->append_sid($url, $params, $is_amp, $session_id);
+}
+
 /**
 * Set config value.
 * Creates missing config entry if update did not succeed and phpbb::$config for this entry empty.
@@ -248,14 +256,14 @@ function markread($mode, $forum_id = false, $topic_id = false, $post_time = 0, $
 	{
 		if ($forum_id === false || !sizeof($forum_id))
 		{
-			if (phpbb::$config['load_db_lastread'] && phpbb::$user->data['is_registered'])
+			if (phpbb::$config['load_db_lastread'] && phpbb::$user->is_registered)
 			{
 				// Mark all forums read (index page)
 				phpbb::$db->sql_query('DELETE FROM ' . TOPICS_TRACK_TABLE . ' WHERE user_id = ' . phpbb::$user->data['user_id']);
 				phpbb::$db->sql_query('DELETE FROM ' . FORUMS_TRACK_TABLE . ' WHERE user_id = ' . phpbb::$user->data['user_id']);
 				phpbb::$db->sql_query('UPDATE ' . USERS_TABLE . ' SET user_lastmark = ' . time() . ' WHERE user_id = ' . phpbb::$user->data['user_id']);
 			}
-			else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->data['is_registered'])
+			else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->is_registered)
 			{
 				$tracking_topics = phpbb_request::variable(phpbb::$config['cookie_name'] . '_track', '', false, phpbb_request::COOKIE);
 				$tracking_topics = ($tracking_topics) ? tracking_unserialize($tracking_topics) : array();
@@ -270,7 +278,7 @@ function markread($mode, $forum_id = false, $topic_id = false, $post_time = 0, $
 
 				unset($tracking_topics);
 
-				if (phpbb::$user->data['is_registered'])
+				if (phpbb::$user->is_registered)
 				{
 					phpbb::$db->sql_query('UPDATE ' . USERS_TABLE . ' SET user_lastmark = ' . time() . ' WHERE user_id = ' . phpbb::$user->data['user_id']);
 				}
@@ -290,7 +298,7 @@ function markread($mode, $forum_id = false, $topic_id = false, $post_time = 0, $
 		// Add 0 to forums array to mark global announcements correctly
 		$forum_id[] = 0;
 
-		if (phpbb::$config['load_db_lastread'] && phpbb::$user->data['is_registered'])
+		if (phpbb::$config['load_db_lastread'] && phpbb::$user->is_registered)
 		{
 			$sql = 'DELETE FROM ' . TOPICS_TRACK_TABLE . '
 				WHERE user_id = ' . phpbb::$user->data['user_id'] . '
@@ -334,7 +342,7 @@ function markread($mode, $forum_id = false, $topic_id = false, $post_time = 0, $
 				phpbb::$db->sql_multi_insert(FORUMS_TRACK_TABLE, $sql_ary);
 			}
 		}
-		else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->data['is_registered'])
+		else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->is_registered)
 		{
 			$tracking = phpbb_request::variable(phpbb::$config['cookie_name'] . '_track', '', false, phpbb_request::COOKIE);
 			$tracking = ($tracking) ? tracking_unserialize($tracking) : array();
@@ -381,7 +389,7 @@ function markread($mode, $forum_id = false, $topic_id = false, $post_time = 0, $
 			return;
 		}
 
-		if (phpbb::$config['load_db_lastread'] && phpbb::$user->data['is_registered'])
+		if (phpbb::$config['load_db_lastread'] && phpbb::$user->is_registered)
 		{
 			$sql = 'UPDATE ' . TOPICS_TRACK_TABLE . '
 				SET mark_time = ' . (($post_time) ? $post_time : time()) . '
@@ -406,7 +414,7 @@ function markread($mode, $forum_id = false, $topic_id = false, $post_time = 0, $
 				phpbb::$db->sql_return_on_error(false);
 			}
 		}
-		else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->data['is_registered'])
+		else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->is_registered)
 		{
 			$tracking = phpbb_request::variable(phpbb::$config['cookie_name'] . '_track', '', false, phpbb_request::COOKIE);
 			$tracking = ($tracking) ? tracking_unserialize($tracking) : array();
@@ -451,7 +459,7 @@ function markread($mode, $forum_id = false, $topic_id = false, $post_time = 0, $
 					}
 				}
 
-				if (phpbb::$user->data['is_registered'])
+				if (phpbb::$user->is_registered)
 				{
 					phpbb::$user->data['user_lastmark'] = intval(base_convert(max($time_keys) + phpbb::$config['board_startdate'], 36, 10));
 					phpbb::$db->sql_query('UPDATE ' . USERS_TABLE . ' SET user_lastmark = ' . phpbb::$user->data['user_lastmark'] . ' WHERE user_id = ' . phpbb::$user->data['user_id']);
@@ -586,7 +594,7 @@ function get_complete_topic_tracking($forum_id, $topic_ids, $global_announce_lis
 		$topic_ids = array($topic_ids);
 	}
 
-	if (phpbb::$config['load_db_lastread'] && phpbb::$user->data['is_registered'])
+	if (phpbb::$config['load_db_lastread'] && phpbb::$user->is_registered)
 	{
 		$sql = 'SELECT topic_id, mark_time
 			FROM ' . TOPICS_TRACK_TABLE . '
@@ -633,7 +641,7 @@ function get_complete_topic_tracking($forum_id, $topic_ids, $global_announce_lis
 			}
 		}
 	}
-	else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->data['is_registered'])
+	else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->is_registered)
 	{
 		global $tracking_topics;
 
@@ -643,7 +651,7 @@ function get_complete_topic_tracking($forum_id, $topic_ids, $global_announce_lis
 			$tracking_topics = ($tracking_topics) ? tracking_unserialize($tracking_topics) : array();
 		}
 
-		if (!phpbb::$user->data['is_registered'])
+		if (!phpbb::$user->is_registered)
 		{
 			$user_lastmark = (isset($tracking_topics['l'])) ? base_convert($tracking_topics['l'], 36, 10) + phpbb::$config['board_startdate'] : 0;
 		}
@@ -717,16 +725,16 @@ function update_forum_tracking_info($forum_id, $forum_last_post_time, $f_mark_ti
 	// Determine the users last forum mark time if not given.
 	if ($mark_time_forum === false)
 	{
-		if (phpbb::$config['load_db_lastread'] && phpbb::$user->data['is_registered'])
+		if (phpbb::$config['load_db_lastread'] && phpbb::$user->is_registered)
 		{
 			$mark_time_forum = (!empty($f_mark_time)) ? $f_mark_time : phpbb::$user->data['user_lastmark'];
 		}
-		else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->data['is_registered'])
+		else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->is_registered)
 		{
 			$tracking_topics = phpbb_request::variable(phpbb::$config['cookie_name'] . '_track', '', false, phpbb_request::COOKIE);
 			$tracking_topics = ($tracking_topics) ? tracking_unserialize($tracking_topics) : array();
 
-			if (!phpbb::$user->data['is_registered'])
+			if (!phpbb::$user->is_registered)
 			{
 				phpbb::$user->data['user_lastmark'] = (isset($tracking_topics['l'])) ? (int) (base_convert($tracking_topics['l'], 36, 10) + phpbb::$config['board_startdate']) : 0;
 			}
@@ -737,7 +745,7 @@ function update_forum_tracking_info($forum_id, $forum_last_post_time, $f_mark_ti
 
 	// Check the forum for any left unread topics.
 	// If there are none, we mark the forum as read.
-	if (phpbb::$config['load_db_lastread'] && phpbb::$user->data['is_registered'])
+	if (phpbb::$config['load_db_lastread'] && phpbb::$user->is_registered)
 	{
 		if ($mark_time_forum >= $forum_last_post_time)
 		{
@@ -758,7 +766,7 @@ function update_forum_tracking_info($forum_id, $forum_last_post_time, $f_mark_ti
 			phpbb::$db->sql_freeresult($result);
 		}
 	}
-	else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->data['is_registered'])
+	else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->is_registered)
 	{
 		// Get information from cookie
 		$row = false;
@@ -1046,7 +1054,7 @@ function on_page($num_items, $per_page, $start)
 function add_form_key($form_name)
 {
 	$now = time();
-	$token_sid = (phpbb::$user->data['user_id'] == ANONYMOUS && !empty(phpbb::$config['form_token_sid_guests'])) ? phpbb::$user->session_id : '';
+	$token_sid = (phpbb::$user->is_guest && !empty(phpbb::$config['form_token_sid_guests'])) ? phpbb::$user->session_id : '';
 	$token = sha1($now . phpbb::$user->data['user_form_salt'] . $form_name . $token_sid);
 
 	$s_fields = build_hidden_fields(array(
@@ -1085,7 +1093,7 @@ function check_form_key($form_name, $timespan = false, $return_page = '', $trigg
 		// If creation_time and the time() now is zero we can assume it was not a human doing this (the check for if ($diff)...
 		if ($diff && ($diff <= $timespan || $timespan === -1))
 		{
-			$token_sid = (phpbb::$user->data['user_id'] == ANONYMOUS && !empty(phpbb::$config['form_token_sid_guests'])) ? phpbb::$user->session_id : '';
+			$token_sid = (phpbb::$user->is_guest && !empty(phpbb::$config['form_token_sid_guests'])) ? phpbb::$user->session_id : '';
 			$key = sha1($creation_time . phpbb::$user->data['user_form_salt'] . $form_name . $token_sid);
 
 			if ($key === $token)
@@ -2103,7 +2111,7 @@ function page_header($page_title = '', $display_online_list = true)
 	if (phpbb::$plugins->function_inject(__FUNCTION__)) phpbb::$plugins->call_inject(__FUNCTION__, array('default', &$page_title, &$display_online_list));
 
 	// Generate logged in/logged out status
-	if (phpbb::$user->data['user_id'] != ANONYMOUS)
+	if (!phpbb::$user->is_guest)
 	{
 		$u_login_logout = phpbb::$url->append_sid('ucp', 'mode=logout', true, phpbb::$user->session_id);
 		$l_login_logout = sprintf(phpbb::$user->lang['LOGOUT_USER'], phpbb::$user->data['username']);
@@ -2115,7 +2123,7 @@ function page_header($page_title = '', $display_online_list = true)
 	}
 
 	// Last visit date/time
-	$s_last_visit = (phpbb::$user->data['user_id'] != ANONYMOUS) ? phpbb::$user->format_date(phpbb::$user->data['session_last_visit']) : '';
+	$s_last_visit = (!phpbb::$user->is_guest) ? phpbb::$user->format_date(phpbb::$user->data['session_last_visit']) : '';
 
 	// Get users online list ... if required
 	$online_userlist = array();
@@ -2253,7 +2261,7 @@ function page_header($page_title = '', $display_online_list = true)
 	$s_privmsg_new = false;
 
 	// Obtain number of new private messages if user is logged in
-	if (!empty(phpbb::$user->data['is_registered']))
+	if (!empty(phpbb::$user->is_registered))
 	{
 		if (phpbb::$user->data['user_new_privmsg'])
 		{
@@ -2288,7 +2296,7 @@ function page_header($page_title = '', $display_online_list = true)
 	}
 
 	// Which timezone?
-	$tz = (phpbb::$user->data['user_id'] != ANONYMOUS) ? strval(doubleval(phpbb::$user->data['user_timezone'])) : strval(doubleval(phpbb::$config['board_timezone']));
+	$tz = (!phpbb::$user->is_guest) ? strval(doubleval(phpbb::$user->data['user_timezone'])) : strval(doubleval(phpbb::$config['board_timezone']));
 
 	// Send a proper content-language to the output
 	$user_lang = phpbb::$user->lang['USER_LANG'];
@@ -2340,10 +2348,10 @@ function page_header($page_title = '', $display_online_list = true)
 		'U_SEARCH_UNANSWERED'	=> phpbb::$url->append_sid('search', 'search_id=unanswered'),
 		'U_SEARCH_ACTIVE_TOPICS'=> phpbb::$url->append_sid('search', 'search_id=active_topics'),
 		'U_DELETE_COOKIES'		=> phpbb::$url->append_sid('ucp', 'mode=delete_cookies'),
-		'U_TEAM'				=> (phpbb::$user->data['user_id'] != ANONYMOUS && !phpbb::$acl->acl_get('u_viewprofile')) ? '' : phpbb::$url->append_sid('memberlist', 'mode=leaders'),
+		'U_TEAM'				=> (!phpbb::$user->is_guest && !phpbb::$acl->acl_get('u_viewprofile')) ? '' : phpbb::$url->append_sid('memberlist', 'mode=leaders'),
 		'U_RESTORE_PERMISSIONS'	=> (phpbb::$user->data['user_perm_from'] && phpbb::$acl->acl_get('a_switchperm')) ? phpbb::$url->append_sid('ucp', 'mode=restore_perm') : '',
 
-		'S_USER_LOGGED_IN'		=> (phpbb::$user->data['user_id'] != ANONYMOUS) ? true : false,
+		'S_USER_LOGGED_IN'		=> (!phpbb::$user->is_guest) ? true : false,
 		'S_AUTOLOGIN_ENABLED'	=> (phpbb::$config['allow_autologin']) ? true : false,
 		'S_BOARD_DISABLED'		=> (phpbb::$config['board_disable']) ? true : false,
 		'S_REGISTERED_USER'		=> (!empty(phpbb::$user->is_registered)) ? true : false,
@@ -2356,10 +2364,10 @@ function page_header($page_title = '', $display_online_list = true)
 		'S_CONTENT_FLOW_BEGIN'	=> (phpbb::$user->lang['DIRECTION'] == 'ltr') ? 'left' : 'right',
 		'S_CONTENT_FLOW_END'	=> (phpbb::$user->lang['DIRECTION'] == 'ltr') ? 'right' : 'left',
 		'S_CONTENT_ENCODING'	=> 'UTF-8',
-		'S_TIMEZONE'			=> (phpbb::$user->data['user_dst'] || (phpbb::$user->data['user_id'] == ANONYMOUS && phpbb::$config['board_dst'])) ? sprintf(phpbb::$user->lang['ALL_TIMES'], phpbb::$user->lang['tz'][$tz], phpbb::$user->lang['tz']['dst']) : sprintf(phpbb::$user->lang['ALL_TIMES'], phpbb::$user->lang['tz'][$tz], ''),
+		'S_TIMEZONE'			=> (phpbb::$user->data['user_dst'] || (phpbb::$user->is_guest && phpbb::$config['board_dst'])) ? sprintf(phpbb::$user->lang['ALL_TIMES'], phpbb::$user->lang['tz'][$tz], phpbb::$user->lang['tz']['dst']) : sprintf(phpbb::$user->lang['ALL_TIMES'], phpbb::$user->lang['tz'][$tz], ''),
 		'S_DISPLAY_ONLINE_LIST'	=> ($l_online_time) ? 1 : 0,
 		'S_DISPLAY_SEARCH'		=> (!phpbb::$config['load_search']) ? 0 : (phpbb::$acl->acl_get('u_search') && phpbb::$acl->acl_getf_global('f_search')),
-		'S_DISPLAY_PM'			=> (phpbb::$config['allow_privmsg'] && !empty(phpbb::$user->data['is_registered']) && (phpbb::$acl->acl_get('u_readpm') || phpbb::$acl->acl_get('u_sendpm'))) ? true : false,
+		'S_DISPLAY_PM'			=> (phpbb::$config['allow_privmsg'] && !empty(phpbb::$user->is_registered) && (phpbb::$acl->acl_get('u_readpm') || phpbb::$acl->acl_get('u_sendpm'))) ? true : false,
 		'S_DISPLAY_MEMBERLIST'	=> (isset($auth)) ? phpbb::$acl->acl_get('u_viewprofile') : 0,
 		'S_NEW_PM'				=> ($s_privmsg_new) ? 1 : 0,
 		'S_REGISTER_ENABLED'	=> (phpbb::$config['require_activation'] != USER_ACTIVATION_DISABLE) ? true : false,
diff --git a/phpBB/includes/functions_content.php b/phpBB/includes/functions_content.php
index 59334545f7..1ef19be8d2 100644
--- a/phpBB/includes/functions_content.php
+++ b/phpBB/includes/functions_content.php
@@ -1191,7 +1191,7 @@ function get_username_string($mode, $user_id, $username, $username_colour = '',
 
 			// Build correct profile url - only show if not anonymous and permission to view profile if registered user
 			// For anonymous the link leads to a login page.
-			if ($user_id && $user_id != ANONYMOUS && (phpbb::$user->data['user_id'] == ANONYMOUS || phpbb::$acl->acl_get('u_viewprofile')))
+			if ($user_id && $user_id != ANONYMOUS && (phpbb::$user->is_guest || phpbb::$acl->acl_get('u_viewprofile')))
 			{
 				$profile_url = ($custom_profile_url !== false) ? $custom_profile_url . '&amp;u=' . (int) $user_id : str_replace(array('={USER_ID}', '=%7BUSER_ID%7D'), '=' . (int) $user_id, $_profile_cache['base_url']);
 			}
diff --git a/phpBB/includes/functions_display.php b/phpBB/includes/functions_display.php
index 19f9716c77..5fe6d39fe1 100644
--- a/phpBB/includes/functions_display.php
+++ b/phpBB/includes/functions_display.php
@@ -144,7 +144,7 @@ function display_forums($root_data = '', $display_moderators = true, $return_mod
 		}
 		else if (phpbb::$config['load_anon_lastread'] || phpbb::$user->is_registered)
 		{
-			if (!phpbb::$user->data['is_registered'])
+			if (!phpbb::$user->is_registered)
 			{
 				phpbb::$user->data['user_lastmark'] = (isset($tracking_topics['l'])) ? (int) (base_convert($tracking_topics['l'], 36, 10) + phpbb::$config['board_startdate']) : 0;
 			}
@@ -701,7 +701,7 @@ function get_moderators(&$forum_moderators, $forum_id = false)
 		{
 			$group_name = (($row['group_type'] == GROUP_SPECIAL) ? phpbb::$user->lang['G_' . $row['group_name']] : $row['group_name']);
 
-			if (phpbb::$user->data['user_id'] != ANONYMOUS && !phpbb::$acl->acl_get('u_viewprofile'))
+			if (!phpbb::$user->is_guest && !phpbb::$acl->acl_get('u_viewprofile'))
 			{
 				$forum_moderators[$row['forum_id']][] = '<span' . (($row['group_colour']) ? ' style="color:#' . $row['group_colour'] . ';"' : '') . '>' . $group_name . '</span>';
 			}
diff --git a/phpBB/index.php b/phpBB/index.php
index 3fd548d11a..0b687f6802 100644
--- a/phpBB/index.php
+++ b/phpBB/index.php
@@ -62,7 +62,7 @@ while ($row = phpbb::$db->sql_fetchrow($result))
 	$colour_text = ($row['group_colour']) ? ' style="color:#' . $row['group_colour'] . '"' : '';
 	$group_name = ($row['group_type'] == GROUP_SPECIAL) ? phpbb::$user->lang['G_' . $row['group_name']] : $row['group_name'];
 
-	if ($row['group_name'] == 'BOTS' || (phpbb::$user->data['user_id'] != ANONYMOUS && !phpbb::$acl->acl_get('u_viewprofile')))
+	if ($row['group_name'] == 'BOTS' || (!phpbb::$user->is_guest && !phpbb::$acl->acl_get('u_viewprofile')))
 	{
 		$legend[] = '<span' . $colour_text . '>' . $group_name . '</span>';
 	}
diff --git a/phpBB/memberlist.php b/phpBB/memberlist.php
index 62212cebc3..a8f359ba1b 100644
--- a/phpBB/memberlist.php
+++ b/phpBB/memberlist.php
@@ -45,7 +45,7 @@ switch ($mode)
 		// Can this user view profiles/memberlist?
 		if (!phpbb::$acl->acl_gets('u_viewprofile', 'a_user', 'a_useradd', 'a_userdel'))
 		{
-			if (phpbb::$user->data['user_id'] != ANONYMOUS)
+			if (!phpbb::$user->is_guest)
 			{
 				trigger_error('NO_VIEW_USERS');
 			}
@@ -574,7 +574,7 @@ switch ($mode)
 			'U_SWITCH_PERMISSIONS'	=> (phpbb::$acl->acl_get('a_switchperm') && phpbb::$user->data['user_id'] != $user_id) ? append_sid('ucp', "mode=switch_perm&amp;u={$user_id}") : '',
 			'U_MCP_QUEUE'			=> (phpbb::$acl->acl_getf_global('m_approve')) ? append_sid('mcp', 'i=queue', true, phpbb::$user->session_id) : '',
 
-			'S_ZEBRA'			=> (phpbb::$user->data['user_id'] != $user_id && phpbb::$user->data['is_registered'] && $zebra_enabled) ? true : false,
+			'S_ZEBRA'			=> (phpbb::$user->data['user_id'] != $user_id && phpbb::$user->is_registered && $zebra_enabled) ? true : false,
 			'U_ADD_FRIEND'		=> (!$friend) ? append_sid('ucp', 'i=zebra&amp;add=' . urlencode(htmlspecialchars_decode($member['username']))) : '',
 			'U_ADD_FOE'			=> (!$foe) ? append_sid('ucp', 'i=zebra&amp;mode=foes&amp;add=' . urlencode(htmlspecialchars_decode($member['username']))) : '',
 			'U_REMOVE_FRIEND'	=> ($friend) ? append_sid('ucp', 'i=zebra&amp;remove=1&amp;usernames[]=' . $user_id) : '',
diff --git a/phpBB/posting.php b/phpBB/posting.php
index 0811a63c15..73417d0ee1 100644
--- a/phpBB/posting.php
+++ b/phpBB/posting.php
@@ -179,7 +179,7 @@ if (phpbb::$user->is_bot)
 // Is the user able to read within this forum?
 if (!phpbb::$acl->acl_get('f_read', $forum_id))
 {
-	if (phpbb::$user->data['user_id'] != ANONYMOUS)
+	if (!phpbb::$user->is_guest)
 	{
 		trigger_error('USER_CANNOT_READ');
 	}
diff --git a/phpBB/search.php b/phpBB/search.php
index c85033ff26..15f9aade93 100644
--- a/phpBB/search.php
+++ b/phpBB/search.php
@@ -560,7 +560,7 @@ if ($keywords || $author || $author_id || $search_id || $submit)
 				}
 			}
 
-			if (phpbb::$config['load_anon_lastread'] || (phpbb::$user->data['is_registered'] && !phpbb::$config['load_db_lastread']))
+			if (phpbb::$config['load_anon_lastread'] || (phpbb::$user->is_registered && !phpbb::$config['load_db_lastread']))
 			{
 				$tracking_topics = phpbb_request::variable(phpbb::$config['cookie_name'] . '_track', '', false, phpbb_request::COOKIE);
 				$tracking_topics = ($tracking_topics) ? tracking_unserialize($tracking_topics) : array();
diff --git a/phpBB/ucp.php b/phpBB/ucp.php
index cc74545eb0..3b519dcfa6 100644
--- a/phpBB/ucp.php
+++ b/phpBB/ucp.php
@@ -81,7 +81,7 @@ switch ($mode)
 	break;
 
 	case 'logout':
-		if (phpbb::$user->data['user_id'] != ANONYMOUS && phpbb_request::variable('sid', '', false, phpbb_request::GET) === phpbb::$user->session_id)
+		if (!phpbb::$user->is_guest && phpbb_request::variable('sid', '', false, phpbb_request::GET) === phpbb::$user->session_id)
 		{
 			phpbb::$user->session_kill();
 			phpbb::$user->session_begin();
@@ -89,7 +89,7 @@ switch ($mode)
 		}
 		else
 		{
-			$message = (phpbb::$user->data['user_id'] == ANONYMOUS) ? phpbb::$user->lang['LOGOUT_REDIRECT'] : phpbb::$user->lang['LOGOUT_FAILED'];
+			$message = (phpbb::$user->is_guest) ? phpbb::$user->lang['LOGOUT_REDIRECT'] : phpbb::$user->lang['LOGOUT_FAILED'];
 		}
 		phpbb::$url->meta_refresh(3, phpbb::$url->append_sid('index'));
 
diff --git a/phpBB/viewtopic.php b/phpBB/viewtopic.php
index 319ba31e1b..16b0f486ae 100644
--- a/phpBB/viewtopic.php
+++ b/phpBB/viewtopic.php
@@ -1583,10 +1583,9 @@ else if (!$all_marked_read)
 /**
 * @todo Do NOT overwrite a request variable.
 */
-// We overwrite the 'f' request variable if there is no forum specified
-// to be able to display the correct online list.
+// We overwrite the 'f' request variable if there is no forum specified to be able to display the correct online list.
 // One downside is that the user currently viewing this topic/post is not taken into account.
-if (empty(phpbb_request::variable('f', '')))
+if (!phpbb_request::variable('f', 0))
 {
 	phpbb_request::overwrite('f', $forum_id);
 }