diff --git a/phpBB/phpbb/attachment/upload.php b/phpBB/phpbb/attachment/upload.php
index 7cd94d0858..ae5a68962d 100644
--- a/phpBB/phpbb/attachment/upload.php
+++ b/phpBB/phpbb/attachment/upload.php
@@ -48,6 +48,9 @@ class upload
 	/** @var dispatcher */
 	protected $phpbb_dispatcher;
 
+	/** @var string */
+	protected $phpbb_root_path;
+
 	/** @var plupload Plupload */
 	protected $plupload;
 
diff --git a/phpBB/phpbb/auth/auth.php b/phpBB/phpbb/auth/auth.php
index f46a21a8ae..55917ea967 100644
--- a/phpBB/phpbb/auth/auth.php
+++ b/phpBB/phpbb/auth/auth.php
@@ -524,19 +524,19 @@ class auth
 			ORDER BY role_id ASC';
 		$result = $db->sql_query($sql);
 
-		$this->role_cache = array();
+		$role_cache = array();
 		while ($row = $db->sql_fetchrow($result))
 		{
-			$this->role_cache[$row['role_id']][$row['auth_option_id']] = (int) $row['auth_setting'];
+			$role_cache[$row['role_id']][$row['auth_option_id']] = (int) $row['auth_setting'];
 		}
 		$db->sql_freeresult($result);
 
-		foreach ($this->role_cache as $role_id => $role_options)
+		foreach ($role_cache as $role_id => $role_options)
 		{
-			$this->role_cache[$role_id] = serialize($role_options);
+			$role_cache[$role_id] = serialize($role_options);
 		}
 
-		$cache->put('_role_cache', $this->role_cache);
+		$cache->put('_role_cache', $role_cache);
 
 		// Now empty user permissions
 		$where_sql = '';
@@ -828,9 +828,9 @@ class auth
 		global $db, $cache;
 
 		// Check if the role-cache is there
-		if (($this->role_cache = $cache->get('_role_cache')) === false)
+		if (($role_cache = $cache->get('_role_cache')) === false)
 		{
-			$this->role_cache = array();
+			$role_cache = array();
 
 			// We pre-fetch roles
 			$sql = 'SELECT *
@@ -840,16 +840,16 @@ class auth
 
 			while ($row = $db->sql_fetchrow($result))
 			{
-				$this->role_cache[$row['role_id']][$row['auth_option_id']] = (int) $row['auth_setting'];
+				$role_cache[$row['role_id']][$row['auth_option_id']] = (int) $row['auth_setting'];
 			}
 			$db->sql_freeresult($result);
 
-			foreach ($this->role_cache as $role_id => $role_options)
+			foreach ($role_cache as $role_id => $role_options)
 			{
-				$this->role_cache[$role_id] = serialize($role_options);
+				$role_cache[$role_id] = serialize($role_options);
 			}
 
-			$cache->put('_role_cache', $this->role_cache);
+			$cache->put('_role_cache', $role_cache);
 		}
 
 		$hold_ary = array();
@@ -865,7 +865,7 @@ class auth
 			// If a role is assigned, assign all options included within this role. Else, only set this one option.
 			if ($row['auth_role_id'])
 			{
-				$hold_ary[$row['forum_id']] = (empty($hold_ary[$row['forum_id']])) ? unserialize($this->role_cache[$row['auth_role_id']]) : $hold_ary[$row['forum_id']] + unserialize($this->role_cache[$row['auth_role_id']]);
+				$hold_ary[$row['forum_id']] = (empty($hold_ary[$row['forum_id']])) ? unserialize($role_cache[$row['auth_role_id']]) : $hold_ary[$row['forum_id']] + unserialize($role_cache[$row['auth_role_id']]);
 			}
 			else
 			{
@@ -890,9 +890,9 @@ class auth
 			{
 				$this->_set_group_hold_ary($hold_ary[$row['forum_id']], $row['auth_option_id'], $row['auth_setting']);
 			}
-			else if (!empty($this->role_cache[$row['auth_role_id']]))
+			else if (!empty($role_cache[$row['auth_role_id']]))
 			{
-				foreach (unserialize($this->role_cache[$row['auth_role_id']]) as $option_id => $setting)
+				foreach (unserialize($role_cache[$row['auth_role_id']]) as $option_id => $setting)
 				{
 					$this->_set_group_hold_ary($hold_ary[$row['forum_id']], $option_id, $setting);
 				}
diff --git a/phpBB/phpbb/config/config.php b/phpBB/phpbb/config/config.php
index c40145b457..c73cbb0490 100644
--- a/phpBB/phpbb/config/config.php
+++ b/phpBB/phpbb/config/config.php
@@ -50,6 +50,7 @@ class config implements \ArrayAccess, \IteratorAggregate, \Countable
 	* @param  string $key The configuration option's name.
 	* @return bool        Whether the configuration option exists.
 	*/
+	#[\ReturnTypeWillChange]
 	public function offsetExists($key)
 	{
 		return isset($this->config[$key]);
@@ -61,6 +62,7 @@ class config implements \ArrayAccess, \IteratorAggregate, \Countable
 	* @param  string $key The configuration option's name.
 	* @return string      The configuration value
 	*/
+	#[\ReturnTypeWillChange]
 	public function offsetGet($key)
 	{
 		return (isset($this->config[$key])) ? $this->config[$key] : '';
@@ -75,6 +77,7 @@ class config implements \ArrayAccess, \IteratorAggregate, \Countable
 	* @param string $key   The configuration option's name.
 	* @param string $value The temporary value.
 	*/
+	#[\ReturnTypeWillChange]
 	public function offsetSet($key, $value)
 	{
 		$this->config[$key] = $value;
@@ -85,6 +88,7 @@ class config implements \ArrayAccess, \IteratorAggregate, \Countable
 	*
 	* @param string $key The configuration option's name.
 	*/
+	#[\ReturnTypeWillChange]
 	public function offsetUnset($key)
 	{
 		trigger_error('Config values have to be deleted explicitly with the \phpbb\config\config::delete($key) method.', E_USER_ERROR);
diff --git a/phpBB/phpbb/datetime.php b/phpBB/phpbb/datetime.php
index e171ac2dd1..095f401f0b 100644
--- a/phpBB/phpbb/datetime.php
+++ b/phpBB/phpbb/datetime.php
@@ -57,6 +57,7 @@ class datetime extends \DateTime
 	* @param boolean $force_absolute Force output of a non relative date
 	* @return string Formatted date time
 	*/
+	#[\ReturnTypeWillChange]
 	public function format($format = '', $force_absolute = false)
 	{
 		$format		= $format ? $format : $this->user->date_format;
diff --git a/phpBB/phpbb/event/data.php b/phpBB/phpbb/event/data.php
index 276ab027f2..ef07ca2d7f 100644
--- a/phpBB/phpbb/event/data.php
+++ b/phpBB/phpbb/event/data.php
@@ -44,21 +44,25 @@ class data extends Event implements \ArrayAccess
 		return array_intersect_key($this->data, array_flip($keys));
 	}
 
+	#[\ReturnTypeWillChange]
 	public function offsetExists($offset)
 	{
 		return isset($this->data[$offset]);
 	}
 
+	#[\ReturnTypeWillChange]
 	public function offsetGet($offset)
 	{
 		return isset($this->data[$offset]) ? $this->data[$offset] : null;
 	}
 
+	#[\ReturnTypeWillChange]
 	public function offsetSet($offset, $value)
 	{
 		$this->data[$offset] = $value;
 	}
 
+	#[\ReturnTypeWillChange]
 	public function offsetUnset($offset)
 	{
 		unset($this->data[$offset]);