diff --git a/phpBB/phpbb/auth/provider/base.php b/phpBB/phpbb/auth/provider/base.php
index 6aab3c2735..97a8b8d4ad 100644
--- a/phpBB/phpbb/auth/provider/base.php
+++ b/phpBB/phpbb/auth/provider/base.php
@@ -23,7 +23,6 @@ abstract class base implements provider_interface
 	*/
 	public function init()
 	{
-		return;
 	}
 
 	/**
@@ -31,7 +30,6 @@ abstract class base implements provider_interface
 	*/
 	public function autologin()
 	{
-		return;
 	}
 
 	/**
@@ -39,7 +37,6 @@ abstract class base implements provider_interface
 	*/
 	public function acp()
 	{
-		return;
 	}
 
 	/**
@@ -47,7 +44,6 @@ abstract class base implements provider_interface
 	*/
 	public function get_acp_template($new_config)
 	{
-		return;
 	}
 
 	/**
@@ -55,7 +51,6 @@ abstract class base implements provider_interface
 	*/
 	public function get_login_data()
 	{
-		return;
 	}
 
 	/**
@@ -63,7 +58,6 @@ abstract class base implements provider_interface
 	*/
 	public function get_auth_link_data($user_id = 0)
 	{
-		return;
 	}
 
 	/**
@@ -71,7 +65,6 @@ abstract class base implements provider_interface
 	*/
 	public function logout($data, $new_session)
 	{
-		return;
 	}
 
 	/**
@@ -79,7 +72,6 @@ abstract class base implements provider_interface
 	*/
 	public function validate_session($user)
 	{
-		return;
 	}
 
 	/**
@@ -87,7 +79,6 @@ abstract class base implements provider_interface
 	*/
 	public function login_link_has_necessary_data(array $login_link_data)
 	{
-		return;
 	}
 
 	/**
@@ -95,7 +86,6 @@ abstract class base implements provider_interface
 	*/
 	public function link_account(array $link_data)
 	{
-		return;
 	}
 
 	/**
@@ -103,6 +93,5 @@ abstract class base implements provider_interface
 	*/
 	public function unlink_account(array $link_data)
 	{
-		return;
 	}
 }
diff --git a/phpBB/phpbb/auth/provider/oauth/oauth.php b/phpBB/phpbb/auth/provider/oauth/oauth.php
index cc84bf5dd7..fa84868939 100644
--- a/phpBB/phpbb/auth/provider/oauth/oauth.php
+++ b/phpBB/phpbb/auth/provider/oauth/oauth.php
@@ -218,7 +218,7 @@ class oauth extends base
 				'oauth_provider_id'	=> (string) $unique_id
 			];
 
-			$sql = 'SELECT user_id 
+			$sql = 'SELECT user_id
 				FROM ' . $this->oauth_account_table . '
 				WHERE ' . $this->db->sql_build_array('SELECT', $data);
 			$result = $this->db->sql_query($sql);
@@ -240,6 +240,7 @@ class oauth extends base
 			 * @var ServiceInterface	service			OAuth service
 			 * @since 3.2.3-RC1
 			 * @changed 3.2.6-RC1						Added redirect_data
+			 * @psalm-var string[] $vars
 			 */
 			$vars = [
 				'row',
@@ -423,8 +424,6 @@ class oauth extends base
 		{
 			return 'LOGIN_LINK_MISSING_DATA';
 		}
-
-		return null;
 	}
 
 	/**
@@ -618,8 +617,8 @@ class oauth extends base
 	 * @param array		$link_data		The same variable given to
 	 * 									{@see \phpbb\auth\provider\provider_interface::link_account}
 	 * @param string	$service_name	The name of the service being used in linking.
-	 * @return string|false				Returns a language constant (string) if an error is encountered,
-	 * 									or false on success.
+	 * @return array|string|false		Returns a language constant (string) if an error is encountered,
+	 * 									an array with error info or false on success.
 	 */
 	protected function link_account_auth_link(array $link_data, $service_name)
 	{
@@ -828,8 +827,8 @@ class oauth extends base
 	 * Sets a redirect to the authorization uri.
 	 *
 	 * @param OAuth1Service|OAuth2Service $service		The external OAuth service
-	 * @return array|false								Array if an error occurred,
-	 *                            						false on success
+	 * @return array									Array if an error occurred,
+	 *													won't return on success
 	 */
 	protected function set_redirect($service)
 	{
@@ -854,6 +853,6 @@ class oauth extends base
 
 		redirect($service->getAuthorizationUri($parameters), false, true);
 
-		return false;
+		return [];
 	}
 }
diff --git a/phpBB/phpbb/auth/provider/oauth/token_storage.php b/phpBB/phpbb/auth/provider/oauth/token_storage.php
index aa84be9635..73eb194b0f 100644
--- a/phpBB/phpbb/auth/provider/oauth/token_storage.php
+++ b/phpBB/phpbb/auth/provider/oauth/token_storage.php
@@ -263,7 +263,7 @@ class token_storage implements TokenStorageInterface
 			$data['session_id']	= $this->user->data['session_id'];
 		}
 
-		return $this->get_state_row($data);
+		return $this->get_state_row($data)['oauth_state'] ?? '';
 	}
 
 	/**
@@ -519,7 +519,7 @@ class token_storage implements TokenStorageInterface
 	 *
 	 * @param array		$data		The SQL WHERE data
 	 * @return array|false			array with the OAuth state row,
-	 *                       		false if the state does not exist
+	 *								false if the state does not exist
 	 */
 	protected function get_state_row($data)
 	{
diff --git a/phpBB/phpbb/auth/provider/provider_interface.php b/phpBB/phpbb/auth/provider/provider_interface.php
index 389f6050f2..43115892be 100644
--- a/phpBB/phpbb/auth/provider/provider_interface.php
+++ b/phpBB/phpbb/auth/provider/provider_interface.php
@@ -25,8 +25,8 @@ interface provider_interface
 	 * Changing to an authentication provider will not be permitted in acp_board
 	 * if there is an error.
 	 *
-	 * @return 	boolean|string 	False if the user is identified, otherwise an
-	 *							error message, or null if not implemented.
+	 * @return 	bool|string|void	False if the user is identified, otherwise an
+	 *								error message, or void if not implemented.
 	 */
 	public function init();
 
@@ -52,8 +52,8 @@ interface provider_interface
 	/**
 	 * Autologin function
 	 *
-	 * @return 	array|null	containing the user row, empty if no auto login
-	 * 						should take place, or null if not implemented.
+	 * @return 	array|void	containing the user row, empty if no auto login
+	 * 						should take place, or void if not implemented.
 	 */
 	public function autologin();
 
@@ -61,7 +61,7 @@ interface provider_interface
 	 * This function is used to output any required fields in the authentication
 	 * admin panel. It also defines any required configuration table fields.
 	 *
-	 * @return	array|null	Returns null if not implemented or an array of the
+	 * @return	array|void	Returns void if not implemented or an array of the
 	 *						configuration fields of the provider.
 	 */
 	public function acp();
@@ -74,7 +74,7 @@ interface provider_interface
 	 *
 	 * @param \phpbb\config\config	$new_config	Contains the new configuration values
 	 * 											that have been set in acp_board.
-	 * @return array|null		Returns null if not implemented or an array with
+	 * @return array|void		Returns void if not implemented or an array with
 	 *							the template file name and an array of the vars
 	 *							that the template needs that must conform to the
 	 *							following example:
@@ -107,8 +107,8 @@ interface provider_interface
 	* Returns an array of data necessary to build custom elements on the login
 	* form.
 	*
-	* @return	array|null	If this function is not implemented on an auth
-	*						provider then it returns null. If it is implemented
+	* @return	array|void	If this function is not implemented on an auth
+	*						provider then it returns void. If it is implemented
 	*						it will return an array of up to four elements of
 	*						which only 'TEMPLATE_FILE'. If 'BLOCK_VAR_NAME' is
 	*						present then 'BLOCK_VARS' must also be present in
@@ -139,8 +139,8 @@ interface provider_interface
 	 * into phpBB.
 	 *
 	 * @param 	array 	$user
-	 * @return 	boolean	true if the given user is authenticated, false if the
-	 * 					session should be closed, or null if not implemented.
+	 * @return 	bool|void	true if the given user is authenticated, false if the
+	 * 					session should be closed, or void if not implemented.
 	 */
 	public function validate_session($user);
 
@@ -151,8 +151,8 @@ interface provider_interface
 	*
 	* @param	array	$login_link_data	Any data needed to link a phpBB account to
 	*								an external account.
-	* @return	string|null	Returns a string with a language constant if there
-	*						is data missing or null if there is no error.
+	* @return	string|void	Returns a string with a language constant if there
+	*						is data missing or void if there is no error.
 	*/
 	public function login_link_has_necessary_data(array $login_link_data);
 
@@ -171,8 +171,8 @@ interface provider_interface
 	*						defaults to 0, which is not a valid ID. The method
 	*						should fall back to the current user's ID in this
 	*						case.
-	* @return	array|null	If this function is not implemented on an auth
-	*						provider then it returns null. If it is implemented
+	* @return	array|void	If this function is not implemented on an auth
+	*						provider then it returns void. If it is implemented
 	*						it will return an array of up to four elements of
 	*						which only 'TEMPLATE_FILE'. If 'BLOCK_VAR_NAME' is
 	*						present then 'BLOCK_VARS' must also be present in
diff --git a/phpBB/phpbb/db/driver/driver.php b/phpBB/phpbb/db/driver/driver.php
index a16c6260f4..da4cc80459 100644
--- a/phpBB/phpbb/db/driver/driver.php
+++ b/phpBB/phpbb/db/driver/driver.php
@@ -571,7 +571,7 @@ abstract class driver implements driver_interface
 	*/
 	function sql_build_array($query, $assoc_ary = [])
 	{
-		if (!count($assoc_ary))
+		if (!is_array($assoc_ary) || !count($assoc_ary))
 		{
 			return false;
 		}