diff --git a/phpBB/includes/functions.php b/phpBB/includes/functions.php
index 030fd17d0c..c5e60b497d 100644
--- a/phpBB/includes/functions.php
+++ b/phpBB/includes/functions.php
@@ -130,7 +130,7 @@ function phpbb_gmgetdate($time = false)
 *
 * @return array|string                    data array if $string_only is false
 */
-function get_formatted_filesize($value, bool $string_only = true, array $allowed_units = null)
+function get_formatted_filesize($value, bool $string_only = true, array|null $allowed_units = null)
 {
 	global $user;
 
@@ -253,7 +253,7 @@ function still_on_time($extra_time = 15)
 * @return mixed				Boolean (true, false) if comparison operator is specified.
 *							Integer (-1, 0, 1) otherwise.
 */
-function phpbb_version_compare(string $version1, string $version2, string $operator = null)
+function phpbb_version_compare(string $version1, string $version2, string|null $operator = null)
 {
 	$version1 = strtolower($version1);
 	$version2 = strtolower($version2);
diff --git a/phpBB/includes/functions_acp.php b/phpBB/includes/functions_acp.php
index a3bae23ab5..3a3dc080d0 100644
--- a/phpBB/includes/functions_acp.php
+++ b/phpBB/includes/functions_acp.php
@@ -215,7 +215,7 @@ function adm_back_link($u_action)
  *
  * @return array
  */
-function build_select(array $options_ary, int|string|bool $option_default = false): array
+function build_select(array $options_ary, bool|int|string $option_default = false): array
 {
 	global $language;
 
diff --git a/phpBB/phpbb/avatar/driver/driver.php b/phpBB/phpbb/avatar/driver/driver.php
index 03c4790a6e..4e6f588f4a 100644
--- a/phpBB/phpbb/avatar/driver/driver.php
+++ b/phpBB/phpbb/avatar/driver/driver.php
@@ -82,7 +82,7 @@ abstract class driver implements \phpbb\avatar\driver\driver_interface
 	* @param \phpbb\path_helper $path_helper phpBB path helper
 	* @param \phpbb\cache\driver\driver_interface|null $cache Cache driver
 	*/
-	public function __construct(\phpbb\config\config $config, \FastImageSize\FastImageSize $imagesize, $phpbb_root_path, $php_ext, \phpbb\path_helper $path_helper, \phpbb\cache\driver\driver_interface $cache = null)
+	public function __construct(\phpbb\config\config $config, \FastImageSize\FastImageSize $imagesize, $phpbb_root_path, $php_ext, \phpbb\path_helper $path_helper, \phpbb\cache\driver\driver_interface|null $cache = null)
 	{
 		$this->config = $config;
 		$this->imagesize = $imagesize;
diff --git a/phpBB/phpbb/ban/type/email.php b/phpBB/phpbb/ban/type/email.php
index 213084fc24..5eef248eb3 100644
--- a/phpBB/phpbb/ban/type/email.php
+++ b/phpBB/phpbb/ban/type/email.php
@@ -28,7 +28,7 @@ class email extends base
 	/**
 	 * {@inheritDoc}
 	 */
-	public function get_user_column(): ?string
+	public function get_user_column(): string|null
 	{
 		return 'user_email';
 	}
diff --git a/phpBB/phpbb/ban/type/ip.php b/phpBB/phpbb/ban/type/ip.php
index 7f8c6ee81d..6dfa807a30 100644
--- a/phpBB/phpbb/ban/type/ip.php
+++ b/phpBB/phpbb/ban/type/ip.php
@@ -31,7 +31,7 @@ class ip extends base
 	/**
 	 * @inheritDoc
 	 */
-	public function get_user_column(): ?string
+	public function get_user_column(): string|null
 	{
 		return null;
 	}
diff --git a/phpBB/phpbb/ban/type/type_interface.php b/phpBB/phpbb/ban/type/type_interface.php
index db86fc8ae7..346b57072e 100644
--- a/phpBB/phpbb/ban/type/type_interface.php
+++ b/phpBB/phpbb/ban/type/type_interface.php
@@ -33,7 +33,7 @@ interface type_interface
 	 *
 	 * @return string|null
 	 */
-	public function get_user_column(): ?string;
+	public function get_user_column(): string|null;
 
 	/**
 	 * Sets a user object to the ban type to have it excluded
diff --git a/phpBB/phpbb/class_loader.php b/phpBB/phpbb/class_loader.php
index 19242049aa..9f115a22ed 100644
--- a/phpBB/phpbb/class_loader.php
+++ b/phpBB/phpbb/class_loader.php
@@ -48,7 +48,7 @@ class class_loader
 	* @param string $php_ext The file extension for PHP files
 	* @param \phpbb\cache\driver\driver_interface|null $cache An implementation of the phpBB cache interface.
 	*/
-	public function __construct($namespace, $path, $php_ext = 'php', \phpbb\cache\driver\driver_interface $cache = null)
+	public function __construct($namespace, $path, $php_ext = 'php', \phpbb\cache\driver\driver_interface|null $cache = null)
 	{
 		if ($namespace[0] !== '\\')
 		{
@@ -69,7 +69,7 @@ class class_loader
 	*
 	* @param \phpbb\cache\driver\driver_interface|null $cache An implementation of the phpBB cache interface.
 	*/
-	public function set_cache(\phpbb\cache\driver\driver_interface $cache = null)
+	public function set_cache(\phpbb\cache\driver\driver_interface|null $cache = null)
 	{
 		if ($cache)
 		{
diff --git a/phpBB/phpbb/composer/exception/runtime_exception.php b/phpBB/phpbb/composer/exception/runtime_exception.php
index adbb67994f..161e203d4b 100644
--- a/phpBB/phpbb/composer/exception/runtime_exception.php
+++ b/phpBB/phpbb/composer/exception/runtime_exception.php
@@ -29,7 +29,7 @@ class runtime_exception extends base
 	 * @param \Exception|null	$previous	The previous runtime_exception used for the runtime_exception chaining.
 	 * @param integer		$code		The Exception code.
 	 */
-	public function __construct($prefix, $message = '', array $parameters = [], \Exception $previous = null, $code = 0)
+	public function __construct($prefix, $message = '', array $parameters = [], \Exception|null $previous = null, $code = 0)
 	{
 		parent::__construct($prefix . $message, $parameters, $previous, $code);
 	}
diff --git a/phpBB/phpbb/composer/extension_manager.php b/phpBB/phpbb/composer/extension_manager.php
index 1e14a7591d..144b8d3c89 100644
--- a/phpBB/phpbb/composer/extension_manager.php
+++ b/phpBB/phpbb/composer/extension_manager.php
@@ -68,7 +68,7 @@ class extension_manager extends manager
 	 * @param string			$root_path			phpBB root path
 	 * @param config|null		$config				Config object
 	 */
-	public function __construct(installer $installer, driver_interface $cache, ext_manager $extension_manager, filesystem $filesystem, $package_type, $exception_prefix, $root_path, config $config = null)
+	public function __construct(installer $installer, driver_interface $cache, ext_manager $extension_manager, filesystem $filesystem, $package_type, $exception_prefix, $root_path, config|null $config = null)
 	{
 		$this->extension_manager = $extension_manager;
 		$this->filesystem = $filesystem;
@@ -86,7 +86,7 @@ class extension_manager extends manager
 	/**
 	 * {@inheritdoc}
 	 */
-	public function pre_install(array $packages, IOInterface $io = null)
+	public function pre_install(array $packages, IOInterface|null $io = null)
 	{
 		$installed_manually = array_intersect(array_keys($this->extension_manager->all_available()), array_keys($packages));
 		if (count($installed_manually) !== 0)
@@ -98,7 +98,7 @@ class extension_manager extends manager
 	/**
 	 * {@inheritdoc}
 	 */
-	public function post_install(array $packages, IOInterface $io = null)
+	public function post_install(array $packages, IOInterface|null $io = null)
 	{
 		if ($this->enable_on_install)
 		{
@@ -127,7 +127,7 @@ class extension_manager extends manager
 	/**
 	 * {@inheritdoc}
 	 */
-	protected function pre_update(array $packages, IOInterface $io = null)
+	protected function pre_update(array $packages, IOInterface|null $io = null)
 	{
 		/** @psalm-suppress InvalidArgument */
 		$io->writeError([['DISABLING_EXTENSIONS', [], 1]]);
@@ -158,7 +158,7 @@ class extension_manager extends manager
 	/**
 	 * {@inheritdoc}
 	 */
-	protected function post_update(array $packages, IOInterface $io = null)
+	protected function post_update(array $packages, IOInterface|null $io = null)
 	{
 		/** @psalm-suppress InvalidArgument */
 		$io->writeError([['ENABLING_EXTENSIONS', [], 1]]);
@@ -184,7 +184,7 @@ class extension_manager extends manager
 	/**
 	 * {@inheritdoc}
 	 */
-	public function remove(array $packages, IOInterface $io = null)
+	public function remove(array $packages, IOInterface|null $io = null)
 	{
 		$packages = $this->normalize_version($packages);
 
@@ -200,7 +200,7 @@ class extension_manager extends manager
 	/**
 	 * {@inheritdoc}
 	 */
-	public function pre_remove(array $packages, IOInterface $io = null)
+	public function pre_remove(array $packages, IOInterface|null $io = null)
 	{
 		if ($this->purge_on_remove)
 		{
diff --git a/phpBB/phpbb/composer/installer.php b/phpBB/phpbb/composer/installer.php
index cd7456baf6..2e7ab9a614 100644
--- a/phpBB/phpbb/composer/installer.php
+++ b/phpBB/phpbb/composer/installer.php
@@ -101,7 +101,7 @@ class installer
 	 * @param request		$request	phpBB request object
 	 * @param config|null		$config		Config object
 	 */
-	public function __construct($root_path, filesystem $filesystem, request $request, config $config = null)
+	public function __construct($root_path, filesystem $filesystem, request $request, config|null $config = null)
 	{
 		if ($config)
 		{
@@ -135,7 +135,7 @@ class installer
 	 *
 	 * @throws runtime_exception
 	 */
-	public function install(array $packages, $whitelist, IOInterface $io = null)
+	public function install(array $packages, $whitelist, IOInterface|null $io = null)
 	{
 		$this->wrap(function() use ($packages, $whitelist, $io) {
 			$this->do_install($packages, $whitelist, $io);
@@ -155,7 +155,7 @@ class installer
 	 * @throws runtime_exception
 	 * @throws JsonValidationException
 	 */
-	protected function do_install(array $packages, $whitelist, io\io_interface $io = null)
+	protected function do_install(array $packages, $whitelist, io\io_interface|null $io = null)
 	{
 		if (!$io)
 		{
@@ -232,7 +232,7 @@ class installer
 	 * @return Composer|PartialComposer
 	 * @throws JsonValidationException
 	 */
-	protected function get_composer(?string $config_file): PartialComposer
+	protected function get_composer(string|null $config_file): PartialComposer
 	{
 		static $composer_factory;
 		if (!$composer_factory)
diff --git a/phpBB/phpbb/composer/io/html_output_formatter.php b/phpBB/phpbb/composer/io/html_output_formatter.php
index a5e2e8cc4a..6914709d51 100644
--- a/phpBB/phpbb/composer/io/html_output_formatter.php
+++ b/phpBB/phpbb/composer/io/html_output_formatter.php
@@ -46,7 +46,7 @@ class html_output_formatter extends \Composer\Console\HtmlOutputFormatter
 	/**
 	 * {@inheritdoc}
 	 */
-	public function format(?string $message): ?string
+	public function format(string|null $message): string|null
 	{
 		$formatted = parent::format($message);
 
diff --git a/phpBB/phpbb/composer/io/web_io.php b/phpBB/phpbb/composer/io/web_io.php
index aac7f06088..b6e9a1b7ff 100644
--- a/phpBB/phpbb/composer/io/web_io.php
+++ b/phpBB/phpbb/composer/io/web_io.php
@@ -28,7 +28,7 @@ class web_io extends BufferIO implements io_interface
 	 * @param int						$verbosity	Verbosity level
 	 * @param OutputFormatterInterface|null	$formatter	Output formatter
 	 */
-	public function __construct(language $language, $input = '', $verbosity = StreamOutput::VERBOSITY_NORMAL, OutputFormatterInterface $formatter = null)
+	public function __construct(language $language, $input = '', $verbosity = StreamOutput::VERBOSITY_NORMAL, OutputFormatterInterface|null $formatter = null)
 	{
 		$this->language = $language;
 
diff --git a/phpBB/phpbb/composer/manager.php b/phpBB/phpbb/composer/manager.php
index e36a32d1e9..13d3491e9f 100644
--- a/phpBB/phpbb/composer/manager.php
+++ b/phpBB/phpbb/composer/manager.php
@@ -74,7 +74,7 @@ class manager implements manager_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function install(array $packages, IOInterface $io = null)
+	public function install(array $packages, IOInterface|null $io = null)
 	{
 		$packages = $this->normalize_version($packages);
 
@@ -103,7 +103,7 @@ class manager implements manager_interface
 	 *                        Each entry may be a name or an array associating a version constraint to a name
 	 * @param IOInterface|null $io IO object used for the output
 	 */
-	protected function pre_install(array $packages, IOInterface $io = null)
+	protected function pre_install(array $packages, IOInterface|null $io = null)
 	{
 	}
 
@@ -114,14 +114,14 @@ class manager implements manager_interface
 	 *                        Each entry may be a name or an array associating a version constraint to a name
 	 * @param IOInterface|null $io IO object used for the output
 	 */
-	protected function post_install(array $packages, IOInterface $io = null)
+	protected function post_install(array $packages, IOInterface|null $io = null)
 	{
 	}
 
 	/**
 	 * {@inheritdoc}
 	 */
-	public function update(array $packages, IOInterface $io = null)
+	public function update(array $packages, IOInterface|null $io = null)
 	{
 		$packages = $this->normalize_version($packages);
 
@@ -148,7 +148,7 @@ class manager implements manager_interface
 	 *                        Each entry may be a name or an array associating a version constraint to a name
 	 * @param IOInterface|null $io IO object used for the output
 	 */
-	protected function pre_update(array $packages, IOInterface $io = null)
+	protected function pre_update(array $packages, IOInterface|null $io = null)
 	{
 	}
 
@@ -159,14 +159,14 @@ class manager implements manager_interface
 	 *                        Each entry may be a name or an array associating a version constraint to a name
 	 * @param IOInterface|null $io IO object used for the output
 	 */
-	protected function post_update(array $packages, IOInterface $io = null)
+	protected function post_update(array $packages, IOInterface|null $io = null)
 	{
 	}
 
 	/**
 	 * {@inheritdoc}
 	 */
-	public function remove(array $packages, IOInterface $io = null)
+	public function remove(array $packages, IOInterface|null $io = null)
 	{
 		$packages = $this->normalize_version($packages);
 
@@ -195,7 +195,7 @@ class manager implements manager_interface
 	 *                        Each entry may be a name or an array associating a version constraint to a name
 	 * @param IOInterface|null $io IO object used for the output
 	 */
-	protected function pre_remove(array $packages, IOInterface $io = null)
+	protected function pre_remove(array $packages, IOInterface|null $io = null)
 	{
 	}
 
@@ -206,7 +206,7 @@ class manager implements manager_interface
 	 *                        Each entry may be a name or an array associating a version constraint to a name
 	 * @param IOInterface|null $io IO object used for the output
 	 */
-	protected function post_remove(array $packages, IOInterface $io = null)
+	protected function post_remove(array $packages, IOInterface|null $io = null)
 	{
 	}
 
diff --git a/phpBB/phpbb/composer/manager_interface.php b/phpBB/phpbb/composer/manager_interface.php
index d14abee8bc..9fda2f66ee 100644
--- a/phpBB/phpbb/composer/manager_interface.php
+++ b/phpBB/phpbb/composer/manager_interface.php
@@ -30,7 +30,7 @@ interface manager_interface
 	 *
 	 * @throws runtime_exception
 	 */
-	public function install(array $packages, IOInterface $io = null);
+	public function install(array $packages, IOInterface|null $io = null);
 
 	/**
 	 * Updates or installs a set of packages
@@ -41,7 +41,7 @@ interface manager_interface
 	 *
 	 * @throws runtime_exception
 	 */
-	public function update(array $packages, IOInterface $io = null);
+	public function update(array $packages, IOInterface|null $io = null);
 
 	/**
 	 * Removes a set of packages
@@ -52,7 +52,7 @@ interface manager_interface
 	 *
 	 * @throws runtime_exception
 	 */
-	public function remove(array $packages, IOInterface $io = null);
+	public function remove(array $packages, IOInterface|null $io = null);
 
 	/**
 	 * Tells whether or not a package is managed by Composer.
diff --git a/phpBB/phpbb/controller/resolver.php b/phpBB/phpbb/controller/resolver.php
index e2d3e2f193..d4daec7eb2 100644
--- a/phpBB/phpbb/controller/resolver.php
+++ b/phpBB/phpbb/controller/resolver.php
@@ -53,7 +53,7 @@ class resolver implements ControllerResolverInterface
 	* @param string $phpbb_root_path Relative path to phpBB root
 	* @param \phpbb\template\template|null $template
 	*/
-	public function __construct(ContainerInterface $container, $phpbb_root_path, \phpbb\template\template $template = null)
+	public function __construct(ContainerInterface $container, $phpbb_root_path, \phpbb\template\template|null $template = null)
 	{
 		$this->container = $container;
 		$this->template = $template;
diff --git a/phpBB/phpbb/datetime.php b/phpBB/phpbb/datetime.php
index 7b9f9c83ac..a52148e609 100644
--- a/phpBB/phpbb/datetime.php
+++ b/phpBB/phpbb/datetime.php
@@ -42,7 +42,7 @@ class datetime extends \DateTime
 	* @param string $time String in a format accepted by strtotime().
 	* @param \DateTimeZone|null $timezone Time zone of the time.
 	*/
-	public function __construct($user, $time = 'now', \DateTimeZone $timezone = null)
+	public function __construct($user, $time = 'now', \DateTimeZone|null $timezone = null)
 	{
 		$this->user	= $user;
 		$timezone	= $timezone ?: $this->user->timezone;
diff --git a/phpBB/phpbb/db/doctrine/connection_factory.php b/phpBB/phpbb/db/doctrine/connection_factory.php
index b692309688..fb24994b3d 100644
--- a/phpBB/phpbb/db/doctrine/connection_factory.php
+++ b/phpBB/phpbb/db/doctrine/connection_factory.php
@@ -73,10 +73,10 @@ class connection_factory
 	public static function get_connection_from_params(
 		string $driver,
 		string $host,
-		?string $user = null,
-		?string $password = null,
-		?string $name = null,
-		?string $port = null): Connection
+		string|null $user = null,
+		string|null $password = null,
+		string|null $name = null,
+		string|null $port = null): Connection
 	{
 		$available_drivers = DriverManager::getAvailableDrivers();
 		if (!in_array($driver, $available_drivers))
diff --git a/phpBB/phpbb/db/doctrine/connection_parameter_factory.php b/phpBB/phpbb/db/doctrine/connection_parameter_factory.php
index f9008616ca..95aa0c189c 100644
--- a/phpBB/phpbb/db/doctrine/connection_parameter_factory.php
+++ b/phpBB/phpbb/db/doctrine/connection_parameter_factory.php
@@ -37,11 +37,11 @@ class connection_parameter_factory
 	 */
 	public static function get_configuration(
 		string $driver,
-		?string $host = null,
-		?string $user = null,
-		?string $password = null,
-		?string $name = null,
-		?string $port = null) : array
+		string|null $host = null,
+		string|null $user = null,
+		string|null $password = null,
+		string|null $name = null,
+		string|null $port = null) : array
 	{
 		$params = [
 			'driver' => $driver,
@@ -73,11 +73,11 @@ class connection_parameter_factory
 	 */
 	private static function build_connection_parameters(
 		array $params,
-		?string $host = null,
-		?string $user = null,
-		?string $password = null,
-		?string $name = null,
-		?string $port = null) : array
+		string|null $host = null,
+		string|null $user = null,
+		string|null $password = null,
+		string|null $name = null,
+		string|null $port = null) : array
 	{
 		if ($params['driver'] === 'pdo_sqlite')
 		{
@@ -120,7 +120,7 @@ class connection_parameter_factory
 	 *
 	 * @return array Doctrine's DBAL configuration for SQLite.
 	 */
-	private static function build_sqlite_parameters(array $params, string $path, ?string $user, ?string $password) : array
+	private static function build_sqlite_parameters(array $params, string $path, string|null $user, string|null $password) : array
 	{
 		$params['path'] = $path;
 
diff --git a/phpBB/phpbb/db/migration/container_aware_migration.php b/phpBB/phpbb/db/migration/container_aware_migration.php
index 3b4b49b04b..405bf6f7e8 100644
--- a/phpBB/phpbb/db/migration/container_aware_migration.php
+++ b/phpBB/phpbb/db/migration/container_aware_migration.php
@@ -29,7 +29,7 @@ abstract class container_aware_migration extends migration implements ContainerA
 	/**
 	 * {@inheritdoc}
 	 */
-	public function setContainer(ContainerInterface $container = null)
+	public function setContainer(ContainerInterface|null $container = null)
 	{
 		$this->container = $container;
 	}
diff --git a/phpBB/phpbb/db/migration/schema_generator.php b/phpBB/phpbb/db/migration/schema_generator.php
index dfbbf3ccbb..0048d8198d 100644
--- a/phpBB/phpbb/db/migration/schema_generator.php
+++ b/phpBB/phpbb/db/migration/schema_generator.php
@@ -240,7 +240,7 @@ class schema_generator
 	 * @param mixed			$data				Array of values to be set.
 	 * @param callable|null	$value_transform	Callback to transform the value being set.
 	 */
-	private static function set_all(&$schema, $data, ?callable $value_transform = null)
+	private static function set_all(&$schema, $data, callable|null $value_transform = null)
 	{
 		$data = (!is_array($data)) ? [$data] : $data;
 		foreach ($data as $key => $change)
@@ -317,7 +317,7 @@ class schema_generator
 	 *
 	 * @return Closure|null The value transformation callback or null if it is not needed.
 	 */
-	private static function get_value_transform(string $change_type, string $schema_type) : ?Closure
+	private static function get_value_transform(string $change_type, string $schema_type) : Closure|null
 	{
 		if ($change_type !== 'add')
 		{
diff --git a/phpBB/phpbb/debug/error_handler.php b/phpBB/phpbb/debug/error_handler.php
index f0a1efa3e3..159d0d36b1 100644
--- a/phpBB/phpbb/debug/error_handler.php
+++ b/phpBB/phpbb/debug/error_handler.php
@@ -24,7 +24,7 @@ class error_handler extends ErrorHandler
 	/**
 	 * @psalm-suppress MethodSignatureMismatch
 	 */
-	public function __construct(BufferingLogger $bootstrappingLogger = null, private readonly bool $debug = false) // phpcs:ignore Generic.CodeAnalysis.UselessOverridingMethod.Found
+	public function __construct(BufferingLogger|null $bootstrappingLogger = null, private readonly bool $debug = false) // phpcs:ignore Generic.CodeAnalysis.UselessOverridingMethod.Found
 	{
 		parent::__construct($bootstrappingLogger, $debug);
 	}
diff --git a/phpBB/phpbb/event/dispatcher.php b/phpBB/phpbb/event/dispatcher.php
index 7b85edf600..472b1dff96 100644
--- a/phpBB/phpbb/event/dispatcher.php
+++ b/phpBB/phpbb/event/dispatcher.php
@@ -52,7 +52,7 @@ class dispatcher extends EventDispatcher implements dispatcher_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function dispatch(object $event, string $eventName = null) : object
+	public function dispatch(object $event, string|null $eventName = null) : object
 	{
 		if ($this->disabled)
 		{
diff --git a/phpBB/phpbb/event/recursive_event_filter_iterator.php b/phpBB/phpbb/event/recursive_event_filter_iterator.php
index f671c474d9..c8734cd6de 100644
--- a/phpBB/phpbb/event/recursive_event_filter_iterator.php
+++ b/phpBB/phpbb/event/recursive_event_filter_iterator.php
@@ -39,7 +39,7 @@ class recursive_event_filter_iterator extends \RecursiveFilterIterator
 	*
 	* @return recursive_event_filter_iterator
 	*/
-	public function getChildren(): ?\RecursiveFilterIterator
+	public function getChildren(): \RecursiveFilterIterator|null
 	{
 		$inner_iterator = $this->getInnerIterator();
 		assert($inner_iterator instanceof \RecursiveIterator);
diff --git a/phpBB/phpbb/exception/http_exception.php b/phpBB/phpbb/exception/http_exception.php
index f22c90128e..f92606cc7c 100644
--- a/phpBB/phpbb/exception/http_exception.php
+++ b/phpBB/phpbb/exception/http_exception.php
@@ -44,7 +44,7 @@ class http_exception extends runtime_exception implements HttpExceptionInterface
 	 * @param array			$headers		Additional headers to set in the response.
 	 * @param integer		$code			The Exception code.
 	 */
-	public function __construct($status_code, $message = "", array $parameters = array(), \Exception $previous = null, array $headers = array(), $code = 0)
+	public function __construct($status_code, $message = "", array $parameters = array(), \Exception|null $previous = null, array $headers = array(), $code = 0)
 	{
 		$this->status_code = $status_code;
 		$this->headers = $headers;
diff --git a/phpBB/phpbb/exception/runtime_exception.php b/phpBB/phpbb/exception/runtime_exception.php
index ccf0d84f32..632e26dec4 100644
--- a/phpBB/phpbb/exception/runtime_exception.php
+++ b/phpBB/phpbb/exception/runtime_exception.php
@@ -35,7 +35,7 @@ class runtime_exception extends \RuntimeException implements exception_interface
 	 * @param \Exception|null	$previous	The previous runtime_exception used for the runtime_exception chaining.
 	 * @param integer		$code		The Exception code.
 	 */
-	public function __construct($message = "", array $parameters = array(), \Exception $previous = null, $code = 0)
+	public function __construct($message = "", array $parameters = array(), \Exception|null $previous = null, $code = 0)
 	{
 		$this->parameters = $parameters;
 
diff --git a/phpBB/phpbb/extension/manager.php b/phpBB/phpbb/extension/manager.php
index adb6d884d1..ffa38be286 100644
--- a/phpBB/phpbb/extension/manager.php
+++ b/phpBB/phpbb/extension/manager.php
@@ -47,7 +47,7 @@ class manager
 	* @param \phpbb\cache\service|null $cache A cache instance or null
 	* @param string $cache_name The name of the cache variable, defaults to _ext
 	*/
-	public function __construct(ContainerInterface $container, \phpbb\db\driver\driver_interface $db, \phpbb\config\config $config, finder_factory $finder_factory, $extension_table, $phpbb_root_path, \phpbb\cache\service $cache = null, $cache_name = '_ext')
+	public function __construct(ContainerInterface $container, \phpbb\db\driver\driver_interface $db, \phpbb\config\config $config, finder_factory $finder_factory, $extension_table, $phpbb_root_path, \phpbb\cache\service|null $cache = null, $cache_name = '_ext')
 	{
 		$this->cache = $cache;
 		$this->cache_name = $cache_name;
diff --git a/phpBB/phpbb/feed/exception/no_feed_exception.php b/phpBB/phpbb/feed/exception/no_feed_exception.php
index af6357b74c..42a9d6b81a 100644
--- a/phpBB/phpbb/feed/exception/no_feed_exception.php
+++ b/phpBB/phpbb/feed/exception/no_feed_exception.php
@@ -15,7 +15,7 @@ namespace phpbb\feed\exception;
 
 class no_feed_exception extends feed_unavailable_exception
 {
-	public function __construct(\Exception $previous = null, $code = 0)
+	public function __construct(\Exception|null $previous = null, $code = 0)
 	{
 		parent::__construct('NO_FEED', array(), $previous, $code);
 	}
diff --git a/phpBB/phpbb/feed/exception/no_forum_exception.php b/phpBB/phpbb/feed/exception/no_forum_exception.php
index a60832957a..0d2be5fe95 100644
--- a/phpBB/phpbb/feed/exception/no_forum_exception.php
+++ b/phpBB/phpbb/feed/exception/no_forum_exception.php
@@ -15,7 +15,7 @@ namespace phpbb\feed\exception;
 
 class no_forum_exception extends feed_unavailable_exception
 {
-	public function __construct($forum_id, \Exception $previous = null, $code = 0)
+	public function __construct($forum_id, \Exception|null $previous = null, $code = 0)
 	{
 		parent::__construct('NO_FORUM', array($forum_id), $previous, $code);
 	}
diff --git a/phpBB/phpbb/feed/exception/no_topic_exception.php b/phpBB/phpbb/feed/exception/no_topic_exception.php
index b961a65d1c..a97186d8a0 100644
--- a/phpBB/phpbb/feed/exception/no_topic_exception.php
+++ b/phpBB/phpbb/feed/exception/no_topic_exception.php
@@ -15,7 +15,7 @@ namespace phpbb\feed\exception;
 
 class no_topic_exception extends feed_unavailable_exception
 {
-	public function __construct($topic_id, \Exception $previous = null, $code = 0)
+	public function __construct($topic_id, \Exception|null $previous = null, $code = 0)
 	{
 		parent::__construct('NO_TOPIC', array($topic_id), $previous, $code);
 	}
diff --git a/phpBB/phpbb/feed/exception/unauthorized_forum_exception.php b/phpBB/phpbb/feed/exception/unauthorized_forum_exception.php
index 4384c7b39b..eb80dd2497 100644
--- a/phpBB/phpbb/feed/exception/unauthorized_forum_exception.php
+++ b/phpBB/phpbb/feed/exception/unauthorized_forum_exception.php
@@ -15,7 +15,7 @@ namespace phpbb\feed\exception;
 
 class unauthorized_forum_exception extends unauthorized_exception
 {
-	public function __construct($forum_id, \Exception $previous = null, $code = 0)
+	public function __construct($forum_id, \Exception|null $previous = null, $code = 0)
 	{
 		parent::__construct('SORRY_AUTH_READ', array($forum_id), $previous, $code);
 	}
diff --git a/phpBB/phpbb/feed/exception/unauthorized_topic_exception.php b/phpBB/phpbb/feed/exception/unauthorized_topic_exception.php
index f49f0a0476..2a758b1b65 100644
--- a/phpBB/phpbb/feed/exception/unauthorized_topic_exception.php
+++ b/phpBB/phpbb/feed/exception/unauthorized_topic_exception.php
@@ -15,7 +15,7 @@ namespace phpbb\feed\exception;
 
 class unauthorized_topic_exception extends unauthorized_exception
 {
-	public function __construct($topic_id, \Exception $previous = null, $code = 0)
+	public function __construct($topic_id, \Exception|null $previous = null, $code = 0)
 	{
 		parent::__construct('SORRY_AUTH_READ_TOPIC', array($topic_id), $previous, $code);
 	}
diff --git a/phpBB/phpbb/files/filespec.php b/phpBB/phpbb/files/filespec.php
index 48e9284f69..3e167fa731 100644
--- a/phpBB/phpbb/files/filespec.php
+++ b/phpBB/phpbb/files/filespec.php
@@ -103,7 +103,7 @@ class filespec
 	 * @param \phpbb\mimetype\guesser|null	$mimetype_guesser Mime type guesser
 	 * @param \phpbb\plupload\plupload|null	$plupload Plupload
 	 */
-	public function __construct(\phpbb\filesystem\filesystem_interface $phpbb_filesystem, language $language, \bantu\IniGetWrapper\IniGetWrapper $php_ini, \FastImageSize\FastImageSize $imagesize, $phpbb_root_path, \phpbb\mimetype\guesser $mimetype_guesser = null, \phpbb\plupload\plupload $plupload = null)
+	public function __construct(\phpbb\filesystem\filesystem_interface $phpbb_filesystem, language $language, \bantu\IniGetWrapper\IniGetWrapper $php_ini, \FastImageSize\FastImageSize $imagesize, $phpbb_root_path, \phpbb\mimetype\guesser|null $mimetype_guesser = null, \phpbb\plupload\plupload|null $plupload = null)
 	{
 		$this->filesystem = $phpbb_filesystem;
 		$this->language = $language;
diff --git a/phpBB/phpbb/files/filespec_storage.php b/phpBB/phpbb/files/filespec_storage.php
index fcda005d7b..5fb71315b2 100644
--- a/phpBB/phpbb/files/filespec_storage.php
+++ b/phpBB/phpbb/files/filespec_storage.php
@@ -86,7 +86,7 @@ class filespec_storage
 	 * @param \phpbb\mimetype\guesser|null	$mimetype_guesser Mime type guesser
 	 * @param \phpbb\plupload\plupload|null	$plupload Plupload
 	 */
-	public function __construct(language $language, \FastImageSize\FastImageSize $imagesize, \phpbb\mimetype\guesser $mimetype_guesser = null, \phpbb\plupload\plupload $plupload = null)
+	public function __construct(language $language, \FastImageSize\FastImageSize $imagesize, \phpbb\mimetype\guesser|null $mimetype_guesser = null, \phpbb\plupload\plupload|null $plupload = null)
 	{
 		$this->language = $language;
 		$this->imagesize = $imagesize;
diff --git a/phpBB/phpbb/filesystem/exception/filesystem_exception.php b/phpBB/phpbb/filesystem/exception/filesystem_exception.php
index 55ea3625a5..6d533705a2 100644
--- a/phpBB/phpbb/filesystem/exception/filesystem_exception.php
+++ b/phpBB/phpbb/filesystem/exception/filesystem_exception.php
@@ -26,7 +26,7 @@ class filesystem_exception extends runtime_exception
 	 * @param \Exception|null	$previous	The previous runtime_exception used for the runtime_exception chaining.
 	 * @param integer			$code		The Exception code.
 	 */
-	public function __construct($message = '', $filename = '', $parameters = array(), \Exception $previous = null, $code = 0)
+	public function __construct($message = '', $filename = '', $parameters = array(), \Exception|null $previous = null, $code = 0)
 	{
 		parent::__construct($message, array_merge(array('filename' => $filename), $parameters), $previous, $code);
 	}
diff --git a/phpBB/phpbb/filesystem/filesystem.php b/phpBB/phpbb/filesystem/filesystem.php
index 6324c5c209..a84c458bb9 100644
--- a/phpBB/phpbb/filesystem/filesystem.php
+++ b/phpBB/phpbb/filesystem/filesystem.php
@@ -293,7 +293,7 @@ class filesystem implements filesystem_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function mirror($origin_dir, $target_dir, \Traversable $iterator = null, $options = array())
+	public function mirror($origin_dir, $target_dir, \Traversable|null $iterator = null, $options = array())
 	{
 		try
 		{
diff --git a/phpBB/phpbb/filesystem/filesystem_interface.php b/phpBB/phpbb/filesystem/filesystem_interface.php
index 0e7967dcfb..11c4141d0d 100644
--- a/phpBB/phpbb/filesystem/filesystem_interface.php
+++ b/phpBB/phpbb/filesystem/filesystem_interface.php
@@ -190,7 +190,7 @@ interface filesystem_interface
 	 * 															The filename which triggered the error can be
 	 * 															retrieved by filesystem_exception::get_filename()
 	 */
-	public function mirror($origin_dir, $target_dir, \Traversable $iterator = null, $options = array());
+	public function mirror($origin_dir, $target_dir, \Traversable|null $iterator = null, $options = array());
 
 	/**
 	 * Creates a directory recursively.
diff --git a/phpBB/phpbb/finder/factory.php b/phpBB/phpbb/finder/factory.php
index 0ce087b061..81b60bcd8b 100644
--- a/phpBB/phpbb/finder/factory.php
+++ b/phpBB/phpbb/finder/factory.php
@@ -33,7 +33,7 @@ class factory
 	* @param string $phpbb_root_path	Path to the phpbb root directory
 	* @param string $php_ext			php file extension
 	*/
-	public function __construct(?service $cache, bool $use_cache, string $phpbb_root_path, string $php_ext)
+	public function __construct(service|null $cache, bool $use_cache, string $phpbb_root_path, string $php_ext)
 	{
 		$this->cache = $cache;
 		$this->use_cache = $use_cache;
diff --git a/phpBB/phpbb/finder/finder.php b/phpBB/phpbb/finder/finder.php
index 7bad84e36d..1bb197a37c 100644
--- a/phpBB/phpbb/finder/finder.php
+++ b/phpBB/phpbb/finder/finder.php
@@ -58,7 +58,7 @@ class finder
 	* @param string $cache_name The name of the cache variable, defaults to
 	*							_ext_finder
 	*/
-	public function __construct(?service $cache, bool $use_cache, string $phpbb_root_path, string $php_ext, string $cache_name = '_ext_finder')
+	public function __construct(service|null $cache, bool $use_cache, string $phpbb_root_path, string $php_ext, string $cache_name = '_ext_finder')
 	{
 		$this->phpbb_root_path = $phpbb_root_path;
 		$this->cache = $cache;
diff --git a/phpBB/phpbb/form/form_helper.php b/phpBB/phpbb/form/form_helper.php
index 7a266f2339..d489150a11 100644
--- a/phpBB/phpbb/form/form_helper.php
+++ b/phpBB/phpbb/form/form_helper.php
@@ -52,7 +52,7 @@ class form_helper
 	 *
 	 * @return array Array containing form_token and creation_time of form token
 	 */
-	public function get_form_tokens(string $form_name, ?int &$now = 0, ?string &$token_sid = '', ?string &$token = ''): array
+	public function get_form_tokens(string $form_name, int|null &$now = 0, string|null &$token_sid = '', string|null &$token = ''): array
 	{
 		$now = time();
 		$token_sid = ($this->user->data['user_id'] == ANONYMOUS && !empty($this->config['form_token_sid_guests'])) ? $this->user->session_id : '';
@@ -71,7 +71,7 @@ class form_helper
 	 * @param int|null $timespan Lifetime of token or null if default value should be used
 	 * @return bool True if form token is valid, false if not
 	 */
-	public function check_form_tokens(string $form_name, ?int $timespan = null): bool
+	public function check_form_tokens(string $form_name, int|null $timespan = null): bool
 	{
 		if ($timespan === null)
 		{
diff --git a/phpBB/phpbb/install/database_task.php b/phpBB/phpbb/install/database_task.php
index 758e511c1a..83bfe8fbfe 100644
--- a/phpBB/phpbb/install/database_task.php
+++ b/phpBB/phpbb/install/database_task.php
@@ -74,7 +74,7 @@ abstract class database_task extends task_base
 	 *
 	 * @return Result|null Result of the query.
 	 */
-	protected function query(string $sql) : ?Result
+	protected function query(string $sql) : Result|null
 	{
 		try
 		{
@@ -95,7 +95,7 @@ abstract class database_task extends task_base
 	 *
 	 * @return Statement|null The prepared statement object or null if preparing failed
 	 */
-	protected function create_prepared_stmt(string $sql): ?Statement
+	protected function create_prepared_stmt(string $sql): Statement|null
 	{
 		try
 		{
@@ -155,7 +155,7 @@ abstract class database_task extends task_base
 	 *
 	 * @return int|null The last insert ID.
 	 */
-	protected function get_last_insert_id() : ?int
+	protected function get_last_insert_id() : int|null
 	{
 		try
 		{
diff --git a/phpBB/phpbb/install/sequential_task.php b/phpBB/phpbb/install/sequential_task.php
index bc389c272d..60af336039 100644
--- a/phpBB/phpbb/install/sequential_task.php
+++ b/phpBB/phpbb/install/sequential_task.php
@@ -38,7 +38,7 @@ trait sequential_task
 	 *
 	 * @throws resource_limit_reached_exception When resources are exhausted.
 	 */
-	protected function execute(config $config, array $data, ?string $counter_name = null) : void
+	protected function execute(config $config, array $data, string|null $counter_name = null) : void
 	{
 		if ($counter_name === null)
 		{
diff --git a/phpBB/phpbb/messenger/method/base.php b/phpBB/phpbb/messenger/method/base.php
index 17213c6b3d..d4d2310ca8 100644
--- a/phpBB/phpbb/messenger/method/base.php
+++ b/phpBB/phpbb/messenger/method/base.php
@@ -119,8 +119,8 @@ abstract class base implements messenger_interface
 		user $user,
 		string $phpbb_root_path,
 		string $template_cache_path,
-		?manager $ext_manager = null,
-		?log_interface $log = null
+		manager|null $ext_manager = null,
+		log_interface|null $log = null
 	)
 	{
 		$this->assets_bag = $assets_bag;
@@ -469,7 +469,7 @@ abstract class base implements messenger_interface
 	 *
 	 * @return void
 	 */
-	protected function set_template_paths(string|array $path_name, string|array $paths): void
+	protected function set_template_paths(array|string $path_name, array|string $paths): void
 	{
 		$this->setup_template();
 		$this->template->set_custom_style($path_name, $paths);
diff --git a/phpBB/phpbb/notification/method/email.php b/phpBB/phpbb/notification/method/email.php
index 07ce0b4f06..d18867927a 100644
--- a/phpBB/phpbb/notification/method/email.php
+++ b/phpBB/phpbb/notification/method/email.php
@@ -91,7 +91,7 @@ class email extends messenger_base
 	*											method additionally checks if the type provides an email template.
 	* @return bool
 	*/
-	public function is_available(type_interface $notification_type = null)
+	public function is_available(type_interface|null $notification_type = null)
 	{
 		return parent::is_available($notification_type) && $this->config['email_enable'] && !empty($this->user->data['user_email']);
 	}
diff --git a/phpBB/phpbb/notification/method/messenger_base.php b/phpBB/phpbb/notification/method/messenger_base.php
index 090cf9c8d9..3f2532c243 100644
--- a/phpBB/phpbb/notification/method/messenger_base.php
+++ b/phpBB/phpbb/notification/method/messenger_base.php
@@ -59,7 +59,7 @@ abstract class messenger_base extends \phpbb\notification\method\base
 	*											only if the type is provided and if it doesn't provide an email template.
 	* @return bool
 	*/
-	public function is_available(type_interface $notification_type = null)
+	public function is_available(type_interface|null $notification_type = null)
 	{
 		return $notification_type === null || $notification_type->get_email_template() !== false;
 	}
diff --git a/phpBB/phpbb/notification/method/webpush.php b/phpBB/phpbb/notification/method/webpush.php
index 25b22d54d8..8923728362 100644
--- a/phpBB/phpbb/notification/method/webpush.php
+++ b/phpBB/phpbb/notification/method/webpush.php
@@ -101,7 +101,7 @@ class webpush extends base implements extended_method_interface
 	/**
 	* {@inheritDoc}
 	*/
-	public function is_available(type_interface $notification_type = null): bool
+	public function is_available(type_interface|null $notification_type = null): bool
 	{
 		return $this->config['webpush_enable']
 			&& $this->config['webpush_vapid_public']
diff --git a/phpBB/phpbb/request/request.php b/phpBB/phpbb/request/request.php
index a28b9df541..b546f6869a 100644
--- a/phpBB/phpbb/request/request.php
+++ b/phpBB/phpbb/request/request.php
@@ -57,7 +57,7 @@ class request implements request_interface
 	* Initialises the request class, that means it stores all input data in {@link $input input}
 	* and then calls {@link \phpbb\request\deactivated_super_global \phpbb\request\deactivated_super_global}
 	*/
-	public function __construct(\phpbb\request\type_cast_helper_interface $type_cast_helper = null, $disable_super_globals = true)
+	public function __construct(\phpbb\request\type_cast_helper_interface|null $type_cast_helper = null, $disable_super_globals = true)
 	{
 		if ($type_cast_helper)
 		{
diff --git a/phpBB/phpbb/routing/resources_locator/default_resources_locator.php b/phpBB/phpbb/routing/resources_locator/default_resources_locator.php
index 8cbf089b2a..12866248ff 100644
--- a/phpBB/phpbb/routing/resources_locator/default_resources_locator.php
+++ b/phpBB/phpbb/routing/resources_locator/default_resources_locator.php
@@ -48,7 +48,7 @@ class default_resources_locator implements resources_locator_interface
 	 * @param string		$environment		Name of the current environment
 	 * @param manager|null	$extension_manager	Extension manager
 	 */
-	public function __construct($phpbb_root_path, $environment, manager $extension_manager = null)
+	public function __construct($phpbb_root_path, $environment, manager|null $extension_manager = null)
 	{
 		$this->phpbb_root_path		= $phpbb_root_path;
 		$this->environment			= $environment;
diff --git a/phpBB/phpbb/search/backend/base.php b/phpBB/phpbb/search/backend/base.php
index 9663c15f65..5d3c8efaa5 100644
--- a/phpBB/phpbb/search/backend/base.php
+++ b/phpBB/phpbb/search/backend/base.php
@@ -316,7 +316,7 @@ abstract class base implements search_backend_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function create_index(int &$post_counter = 0): ?array
+	public function create_index(int &$post_counter = 0): array|null
 	{
 		$max_post_id = $this->get_max_post_id();
 		$forums_indexing_enabled = $this->forum_ids_with_indexing_enabled();
@@ -377,7 +377,7 @@ abstract class base implements search_backend_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function delete_index(int &$post_counter = null): ?array
+	public function delete_index(int|null &$post_counter = null): array|null
 	{
 		$max_post_id = $this->get_max_post_id();
 
diff --git a/phpBB/phpbb/search/backend/fulltext_mysql.php b/phpBB/phpbb/search/backend/fulltext_mysql.php
index 7635b503fa..977003d351 100644
--- a/phpBB/phpbb/search/backend/fulltext_mysql.php
+++ b/phpBB/phpbb/search/backend/fulltext_mysql.php
@@ -912,7 +912,7 @@ class fulltext_mysql extends base implements search_backend_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function create_index(int &$post_counter = 0): ?array
+	public function create_index(int &$post_counter = 0): array|null
 	{
 		// Make sure we can actually use MySQL with fulltext indexes
 		if ($error = $this->init())
@@ -984,7 +984,7 @@ class fulltext_mysql extends base implements search_backend_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function delete_index(int &$post_counter = null): ?array
+	public function delete_index(int|null &$post_counter = null): array|null
 	{
 		// Make sure we can actually use MySQL with fulltext indexes
 		if ($error = $this->init())
diff --git a/phpBB/phpbb/search/backend/fulltext_native.php b/phpBB/phpbb/search/backend/fulltext_native.php
index ffdcbff3db..3be1e935f0 100644
--- a/phpBB/phpbb/search/backend/fulltext_native.php
+++ b/phpBB/phpbb/search/backend/fulltext_native.php
@@ -1621,7 +1621,7 @@ class fulltext_native extends base implements search_backend_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function delete_index(int &$post_counter = null): ?array
+	public function delete_index(int|null &$post_counter = null): array|null
 	{
 		$truncate_tables = [
 			$this->search_wordlist_table,
diff --git a/phpBB/phpbb/search/backend/fulltext_postgres.php b/phpBB/phpbb/search/backend/fulltext_postgres.php
index 6c4ac05932..9e1962f9e9 100644
--- a/phpBB/phpbb/search/backend/fulltext_postgres.php
+++ b/phpBB/phpbb/search/backend/fulltext_postgres.php
@@ -867,7 +867,7 @@ class fulltext_postgres extends base implements search_backend_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function create_index(int &$post_counter = 0): ?array
+	public function create_index(int &$post_counter = 0): array|null
 	{
 		// Make sure we can actually use PostgreSQL with fulltext indexes
 		if ($error = $this->init())
@@ -926,7 +926,7 @@ class fulltext_postgres extends base implements search_backend_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function delete_index(int &$post_counter = null): ?array
+	public function delete_index(int|null &$post_counter = null): array|null
 	{
 		// Make sure we can actually use PostgreSQL with fulltext indexes
 		if ($error = $this->init())
diff --git a/phpBB/phpbb/search/backend/fulltext_sphinx.php b/phpBB/phpbb/search/backend/fulltext_sphinx.php
index 93b0c1c522..aa7e0b94fe 100644
--- a/phpBB/phpbb/search/backend/fulltext_sphinx.php
+++ b/phpBB/phpbb/search/backend/fulltext_sphinx.php
@@ -629,7 +629,7 @@ class fulltext_sphinx implements search_backend_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function create_index(int &$post_counter = 0): ?array
+	public function create_index(int &$post_counter = 0): array|null
 	{
 		if (!$this->index_created())
 		{
@@ -656,7 +656,7 @@ class fulltext_sphinx implements search_backend_interface
 	/**
 	 * {@inheritdoc}
 	*/
-	public function delete_index(int &$post_counter = null): ?array
+	public function delete_index(int|null &$post_counter = null): array|null
 	{
 		if ($this->index_created())
 		{
diff --git a/phpBB/phpbb/search/backend/search_backend_interface.php b/phpBB/phpbb/search/backend/search_backend_interface.php
index 82ea0d03ff..b620ef98c0 100644
--- a/phpBB/phpbb/search/backend/search_backend_interface.php
+++ b/phpBB/phpbb/search/backend/search_backend_interface.php
@@ -163,7 +163,7 @@ interface search_backend_interface
 	 * @param int $post_counter
 	 * @return array|null array with current status or null if finished
 	 */
-	public function create_index(int &$post_counter = 0): ?array;
+	public function create_index(int &$post_counter = 0): array|null;
 
 	/**
 	 * Drop fulltext index
@@ -171,7 +171,7 @@ interface search_backend_interface
 	 * @param int $post_counter
 	 * @return array|null array with current status or null if finished
 	 */
-	public function delete_index(int &$post_counter = 0): ?array;
+	public function delete_index(int &$post_counter = 0): array|null;
 
 	/**
 	 * Returns true if both FULLTEXT indexes exist
diff --git a/phpBB/phpbb/search/backend/sphinx/config.php b/phpBB/phpbb/search/backend/sphinx/config.php
index 2dac3a8687..d9ba56a5f2 100644
--- a/phpBB/phpbb/search/backend/sphinx/config.php
+++ b/phpBB/phpbb/search/backend/sphinx/config.php
@@ -28,7 +28,7 @@ class config
 	* @param	string 					$name	The name of the section that shall be returned
 	* @return	config_section|null		The section object or null if none was found
 	*/
-	public function get_section_by_name(string $name): ?config_section
+	public function get_section_by_name(string $name): config_section|null
 	{
 		for ($i = 0, $size = count($this->sections); $i < $size; $i++)
 		{
diff --git a/phpBB/phpbb/search/backend/sphinx/config_section.php b/phpBB/phpbb/search/backend/sphinx/config_section.php
index a3f522209f..eff5bb2953 100644
--- a/phpBB/phpbb/search/backend/sphinx/config_section.php
+++ b/phpBB/phpbb/search/backend/sphinx/config_section.php
@@ -60,7 +60,7 @@ class config_section extends config_item
 	* @return	config_variable|null	The first variable object from this section with the
 	*										given name or null if none was found
 	*/
-	public function get_variable_by_name(string $name): ?config_variable
+	public function get_variable_by_name(string $name): config_variable|null
 	{
 		for ($i = 0, $size = count($this->variables); $i < $size; $i++)
 		{
diff --git a/phpBB/phpbb/storage/exception/storage_exception.php b/phpBB/phpbb/storage/exception/storage_exception.php
index 205cf82561..b7635218a3 100644
--- a/phpBB/phpbb/storage/exception/storage_exception.php
+++ b/phpBB/phpbb/storage/exception/storage_exception.php
@@ -26,7 +26,7 @@ class storage_exception extends runtime_exception
 	 * @param \Exception|null	$previous	The previous runtime_exception used for the runtime_exception chaining
 	 * @param integer			$code		The Exception code
 	 */
-	public function __construct($message = '', $filename = '', $parameters = [], \Exception $previous = null, $code = 0)
+	public function __construct($message = '', $filename = '', $parameters = [], \Exception|null $previous = null, $code = 0)
 	{
 		parent::__construct($message, array_merge(array('filename' => $filename), $parameters), $previous, $code);
 	}
diff --git a/phpBB/phpbb/template/twig/environment.php b/phpBB/phpbb/template/twig/environment.php
index 68d3e9ad89..a5af650c66 100644
--- a/phpBB/phpbb/template/twig/environment.php
+++ b/phpBB/phpbb/template/twig/environment.php
@@ -66,7 +66,7 @@ class environment extends \Twig\Environment
 	* @param dispatcher_interface|null	$phpbb_dispatcher	Event dispatcher object
 	* @param array $options Array of options to pass to Twig
 	*/
-	public function __construct(assets_bag $assets_bag, config $phpbb_config, filesystem $filesystem, path_helper $path_helper, $cache_path, manager $extension_manager = null, LoaderInterface $loader = null, dispatcher_interface $phpbb_dispatcher = null, $options = array())
+	public function __construct(assets_bag $assets_bag, config $phpbb_config, filesystem $filesystem, path_helper $path_helper, $cache_path, manager|null $extension_manager = null, LoaderInterface|null $loader = null, dispatcher_interface|null $phpbb_dispatcher = null, $options = array())
 	{
 		$this->phpbb_config = $phpbb_config;
 
@@ -271,7 +271,7 @@ class environment extends \Twig\Environment
 	* @return \Twig\Template A template instance representing the given template name
 	* @throws \Twig\Error\LoaderError
 	*/
-	public function loadTemplate(string $cls, string $name, int $index = null) : \Twig\Template
+	public function loadTemplate(string $cls, string $name, int|null $index = null) : \Twig\Template
 	{
 		if (strpos($name, '@') === false)
 		{
diff --git a/phpBB/phpbb/template/twig/extension/avatar.php b/phpBB/phpbb/template/twig/extension/avatar.php
index 238caddaf5..e10330301e 100644
--- a/phpBB/phpbb/template/twig/extension/avatar.php
+++ b/phpBB/phpbb/template/twig/extension/avatar.php
@@ -70,7 +70,7 @@ class avatar extends AbstractExtension
 	 *
 	 * @return string	The avatar HTML for the specified mode
 	 */
-	public function get_avatar(environment $environment, string $mode, array $row, ?string $alt, ?bool $ignore_config, ?bool $lazy): string
+	public function get_avatar(environment $environment, string $mode, array $row, string|null $alt, bool|null $ignore_config, bool|null $lazy): string
 	{
 		$alt = $alt ?? false;
 		$ignore_config = $ignore_config ?? false;
diff --git a/phpBB/phpbb/template/twig/twig.php b/phpBB/phpbb/template/twig/twig.php
index 1259618175..aba1d3d099 100644
--- a/phpBB/phpbb/template/twig/twig.php
+++ b/phpBB/phpbb/template/twig/twig.php
@@ -70,9 +70,9 @@ class twig extends \phpbb\template\base
 		\phpbb\template\context $context,
 		environment $twig_environment,
 		$cache_path,
-		\phpbb\user $user = null,
+		\phpbb\user|null $user = null,
 		$extensions = [],
-		\phpbb\extension\manager $extension_manager = null
+		\phpbb\extension\manager|null $extension_manager = null
 	)
 	{
 		$this->path_helper = $path_helper;
diff --git a/phpBB/phpbb/user.php b/phpBB/phpbb/user.php
index c486161a05..f3f4cd04c4 100644
--- a/phpBB/phpbb/user.php
+++ b/phpBB/phpbb/user.php
@@ -709,7 +709,7 @@ class user extends \phpbb\session
 	* @param ?\DateTimeZone $timezone Time zone of the time.
 	* @return \phpbb\datetime Date time object linked to the current users locale
 	*/
-	public function create_datetime(string $time = 'now', ?\DateTimeZone $timezone = null)
+	public function create_datetime(string $time = 'now', \DateTimeZone|null $timezone = null)
 	{
 		$timezone = $timezone ?: $this->create_timezone();
 		return new $this->datetime($this, $time, $timezone);
@@ -723,7 +723,7 @@ class user extends \phpbb\session
 	* @param	?\DateTimeZone	$timezone	Timezone of the date/time, falls back to timezone of current user
 	* @return	string|false			Returns the unix timestamp or false if date is invalid
 	*/
-	public function get_timestamp_from_format($format, $time, ?\DateTimeZone $timezone = null)
+	public function get_timestamp_from_format($format, $time, \DateTimeZone|null $timezone = null)
 	{
 		$timezone = $timezone ?: $this->create_timezone();
 		$date = \DateTime::createFromFormat($format, $time, $timezone);
diff --git a/tests/mock/container_builder.php b/tests/mock/container_builder.php
index 9200ed0767..b6676df3f5 100644
--- a/tests/mock/container_builder.php
+++ b/tests/mock/container_builder.php
@@ -56,7 +56,7 @@ class phpbb_mock_container_builder implements ContainerInterface
 	*
 	* @api
 	*/
-	public function get(string $id, int $invalidBehavior = self::EXCEPTION_ON_INVALID_REFERENCE): ?object
+	public function get(string $id, int $invalidBehavior = self::EXCEPTION_ON_INVALID_REFERENCE): object|null
 	{
 		if ($this->has($id))
 		{
diff --git a/tests/mock/search_backend_mock.php b/tests/mock/search_backend_mock.php
index 84dd26385e..33579ee557 100644
--- a/tests/mock/search_backend_mock.php
+++ b/tests/mock/search_backend_mock.php
@@ -82,13 +82,13 @@ class search_backend_mock implements search_backend_interface
 		// Nothing
 	}
 
-	public function create_index(int &$post_counter = 0): ?array
+	public function create_index(int &$post_counter = 0): array|null
 	{
 		$this->index_created = true;
 		return null;
 	}
 
-	public function delete_index(int &$post_counter = 0): ?array
+	public function delete_index(int &$post_counter = 0): array|null
 	{
 		$this->index_created = true;
 		return null;
diff --git a/tests/profilefields/type_date_test.php b/tests/profilefields/type_date_test.php
index 75de0773d2..480b03baf0 100644
--- a/tests/profilefields/type_date_test.php
+++ b/tests/profilefields/type_date_test.php
@@ -221,7 +221,7 @@ class phpbb_profilefield_type_date_test extends phpbb_test_case
 		return implode('-', func_get_args());
 	}
 
-	public function create_datetime_callback($time = 'now', \DateTimeZone $timezone = null)
+	public function create_datetime_callback($time = 'now', \DateTimeZone|null $timezone = null)
 	{
 		$timezone = $timezone ?: $this->user->timezone;
 		return new \phpbb\datetime($this->user, $time, $timezone);
diff --git a/tests/test_framework/phpbb_test_case_helpers.php b/tests/test_framework/phpbb_test_case_helpers.php
index 3bb279c25f..d3adcceedd 100644
--- a/tests/test_framework/phpbb_test_case_helpers.php
+++ b/tests/test_framework/phpbb_test_case_helpers.php
@@ -346,7 +346,7 @@ class phpbb_test_case_helpers
 	* @param  string             $styles_path Path to the styles dir
 	* @return ContainerInterface
 	*/
-	public function set_s9e_services(ContainerInterface $container = null, $fixture = null, $styles_path = null)
+	public function set_s9e_services(ContainerInterface|null $container = null, $fixture = null, $styles_path = null)
 	{
 		static $first_run;
 		global $config, $phpbb_container, $phpbb_dispatcher, $phpbb_root_path, $phpEx, $request, $user;