diff --git a/phpBB/phpbb/controller/resolver.php b/phpBB/phpbb/controller/resolver.php
index 1e65b2324b..087c1e89b9 100644
--- a/phpBB/phpbb/controller/resolver.php
+++ b/phpBB/phpbb/controller/resolver.php
@@ -65,10 +65,10 @@ class resolver implements ControllerResolverInterface
 	* Load a controller callable
 	*
 	* @param Request $request Symfony Request object
-	* @return false|Callable Callable or false (fixme: method is returning an array)
+	* @return callable|false Callable or false
 	* @throws \phpbb\controller\exception
 	*/
-	public function getController(Request $request)
+	public function getController(Request $request): callable|false
 	{
 		$controller = $request->attributes->get('_controller');
 
diff --git a/phpBB/phpbb/di/extension/config.php b/phpBB/phpbb/di/extension/config.php
index 775de380ec..2b73a4871a 100644
--- a/phpBB/phpbb/di/extension/config.php
+++ b/phpBB/phpbb/di/extension/config.php
@@ -60,7 +60,7 @@ class config extends Extension
 	*
 	* @return string The alias
 	*/
-	public function getAlias()
+	public function getAlias(): string
 	{
 		return 'config';
 	}
diff --git a/phpBB/phpbb/di/extension/core.php b/phpBB/phpbb/di/extension/core.php
index c0725942be..41b510ba2b 100644
--- a/phpBB/phpbb/di/extension/core.php
+++ b/phpBB/phpbb/di/extension/core.php
@@ -144,7 +144,7 @@ class core extends Extension
 	 *
 	 * @return string The alias
 	 */
-	public function getAlias()
+	public function getAlias(): string
 	{
 		return 'core';
 	}
diff --git a/phpBB/phpbb/di/extension/tables.php b/phpBB/phpbb/di/extension/tables.php
index 40684b6038..fc3d9e75c6 100644
--- a/phpBB/phpbb/di/extension/tables.php
+++ b/phpBB/phpbb/di/extension/tables.php
@@ -52,7 +52,7 @@ class tables extends Extension
 	 *
 	 * @return string The alias
 	 */
-	public function getAlias()
+	public function getAlias(): string
 	{
 		return 'tables';
 	}
diff --git a/phpBB/phpbb/exception/http_exception.php b/phpBB/phpbb/exception/http_exception.php
index cae4a282d4..f22c90128e 100644
--- a/phpBB/phpbb/exception/http_exception.php
+++ b/phpBB/phpbb/exception/http_exception.php
@@ -25,14 +25,14 @@ class http_exception extends runtime_exception implements HttpExceptionInterface
 	 *
 	 * @var integer
 	 */
-	private $status_code;
+	private int $status_code;
 
 	/**
 	 * Additional headers to set in the response.
 	 *
 	 * @var array
 	 */
-	private $headers;
+	private array $headers;
 
 	/**
 	 * Constructor
@@ -55,7 +55,7 @@ class http_exception extends runtime_exception implements HttpExceptionInterface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function getStatusCode()
+	public function getStatusCode(): int
 	{
 		return $this->status_code;
 	}
@@ -63,7 +63,7 @@ class http_exception extends runtime_exception implements HttpExceptionInterface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function getHeaders()
+	public function getHeaders(): array
 	{
 		return $this->headers;
 	}
diff --git a/phpBB/phpbb/extension/di/extension_base.php b/phpBB/phpbb/extension/di/extension_base.php
index fcc358dd79..45ed5c4c19 100644
--- a/phpBB/phpbb/extension/di/extension_base.php
+++ b/phpBB/phpbb/extension/di/extension_base.php
@@ -132,7 +132,7 @@ class extension_base extends Extension
 	 *
 	 * @return string The alias
 	 */
-	public function getAlias()
+	public function getAlias(): string
 	{
 		return str_replace('/', '_', $this->extension_name);
 	}
diff --git a/phpBB/phpbb/routing/loader_resolver.php b/phpBB/phpbb/routing/loader_resolver.php
index 13fbc6405c..de3adcaa34 100644
--- a/phpBB/phpbb/routing/loader_resolver.php
+++ b/phpBB/phpbb/routing/loader_resolver.php
@@ -33,7 +33,7 @@ class loader_resolver implements LoaderResolverInterface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function resolve($resource, $type = null)
+	public function resolve($resource, $type = null): false|\Symfony\Component\Config\Loader\LoaderInterface
 	{
 		/** @var \Symfony\Component\Config\Loader\LoaderInterface $loader */
 		foreach ($this->loaders as $loader)
diff --git a/phpBB/phpbb/routing/router.php b/phpBB/phpbb/routing/router.php
index e6f887cca7..18d32ca12b 100644
--- a/phpBB/phpbb/routing/router.php
+++ b/phpBB/phpbb/routing/router.php
@@ -171,7 +171,7 @@ class router implements RouterInterface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function getContext()
+	public function getContext(): RequestContext
 	{
 		return $this->context;
 	}
@@ -179,7 +179,7 @@ class router implements RouterInterface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function generate($name, $parameters = array(), $referenceType = self::ABSOLUTE_PATH)
+	public function generate(string $name, array $parameters = [], int $referenceType = self::ABSOLUTE_PATH): string
 	{
 		return $this->get_generator()->generate($name, $parameters, $referenceType);
 	}
@@ -187,7 +187,7 @@ class router implements RouterInterface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function match($pathinfo)
+	public function match(string $pathinfo): array
 	{
 		return $this->get_matcher()->match($pathinfo);
 	}
diff --git a/tests/console/cron/cron_list_test.php b/tests/console/cron/cron_list_test.php
index 0c1b8b1ccc..cdda4fb886 100644
--- a/tests/console/cron/cron_list_test.php
+++ b/tests/console/cron/cron_list_test.php
@@ -97,7 +97,8 @@ class phpbb_console_command_cron_list_test extends phpbb_test_case
 		);
 
 		$mock_container = new phpbb_mock_container_builder();
-		$mock_container->set('cron.task_collection', []);
+		$task_collection = new \phpbb\di\service_collection($mock_container);
+		$mock_container->set('cron.task_collection', $task_collection);
 
 		$this->cron_manager = new \phpbb\cron\manager($mock_container, $routing_helper, $phpbb_root_path, $pathEx, null);
 		$this->cron_manager->load_tasks($tasks);
diff --git a/tests/console/cron/run_test.php b/tests/console/cron/run_test.php
index 7de1b3455e..90fa2a9fd0 100644
--- a/tests/console/cron/run_test.php
+++ b/tests/console/cron/run_test.php
@@ -74,7 +74,8 @@ class phpbb_console_command_cron_run_test extends phpbb_database_test_case
 		);
 
 		$mock_container = new phpbb_mock_container_builder();
-		$mock_container->set('cron.task_collection', []);
+		$task_collection = new \phpbb\di\service_collection($mock_container);
+		$mock_container->set('cron.task_collection', $task_collection);
 
 		$this->cron_manager = new \phpbb\cron\manager($mock_container, $routing_helper, $phpbb_root_path, $phpEx, null);
 		$this->cron_manager->load_tasks($tasks);
@@ -152,7 +153,8 @@ class phpbb_console_command_cron_run_test extends phpbb_database_test_case
 		);
 
 		$mock_container = new phpbb_mock_container_builder();
-		$mock_container->set('cron.task_collection', []);
+		$task_collection = new \phpbb\di\service_collection($mock_container);
+		$mock_container->set('cron.task_collection', $task_collection);
 
 		$this->cron_manager = new \phpbb\cron\manager($mock_container, $routing_helper, $phpbb_root_path, $phpEx, null);
 		$this->cron_manager->load_tasks($tasks);
@@ -199,7 +201,8 @@ class phpbb_console_command_cron_run_test extends phpbb_database_test_case
 		);
 
 		$mock_container = new phpbb_mock_container_builder();
-		$mock_container->set('cron.task_collection', []);
+		$task_collection = new \phpbb\di\service_collection($mock_container);
+		$mock_container->set('cron.task_collection', $task_collection);
 
 		$this->cron_manager = new \phpbb\cron\manager($mock_container, $routing_helper, $phpbb_root_path, $phpEx, null);
 		$this->cron_manager->load_tasks($tasks);
diff --git a/tests/cron/manager_test.php b/tests/cron/manager_test.php
index 658980d0c5..45736e82fe 100644
--- a/tests/cron/manager_test.php
+++ b/tests/cron/manager_test.php
@@ -105,7 +105,8 @@ class phpbb_cron_manager_test extends \phpbb_test_case
 		);
 
 		$mock_container = new phpbb_mock_container_builder();
-		$mock_container->set('cron.task_collection', []);
+		$task_collection = new \phpbb\di\service_collection($mock_container);
+		$mock_container->set('cron.task_collection', $task_collection);
 
 		$cron_manager = new \phpbb\cron\manager($mock_container, $routing_helper, $phpbb_root_path, $phpEx, null);
 		$cron_manager->load_tasks($tasks);
diff --git a/tests/functional/acp_smilies_test.php b/tests/functional/acp_smilies_test.php
index ebe8717fa7..c24b884dd0 100644
--- a/tests/functional/acp_smilies_test.php
+++ b/tests/functional/acp_smilies_test.php
@@ -38,6 +38,6 @@ class phpbb_functional_acp_smilies_test extends phpbb_functional_test_case
 		$crawler = self::submit($form);
 
 		$html = $crawler->filter('#preview')->html();
-		$this->assertRegexp('(<img [^>]+ alt="&gt;:D" title="&gt;:D"[^>]*>)', $html);
+		$this->assertRegexp('(<img [^>]+ alt=">:D" title=">:D"[^>]*>)', $html);
 	}
 }
diff --git a/tests/functional/extension_controller_test.php b/tests/functional/extension_controller_test.php
index c235278d9d..b4518cfa23 100644
--- a/tests/functional/extension_controller_test.php
+++ b/tests/functional/extension_controller_test.php
@@ -106,6 +106,7 @@ class phpbb_functional_extension_controller_test extends phpbb_functional_test_c
 		$crawler = self::request('GET', 'app.php/foo/baz', array(), false);
 		$this->assert_response_html(500);
 		$this->assertStringContainsString('Controller "foo\bar\controller\controller::baz()" requires that you provide a value for the "$test" argument', $crawler->filter('body')->text());
+		$this->phpbb_extension_manager->purge('foo/bar');
 	}
 
 	/**
diff --git a/tests/functional/ucp_attachments_test.php b/tests/functional/ucp_attachments_test.php
index dad085498d..fbd352ea28 100644
--- a/tests/functional/ucp_attachments_test.php
+++ b/tests/functional/ucp_attachments_test.php
@@ -134,7 +134,7 @@ class phpbb_functional_ucp_attachments_test extends phpbb_functional_test_case
 		$attachment_filename = $crawler->filter('.attachment-filename');
 		$this->assertEquals('valid.jpg', $attachment_filename->attr('title'));
 		$this->assertStringContainsString('app.php/download/attachment/' . $attach_id . '/valid.jpg', $attachment_filename->attr('href'));
-		$this->assertEquals('', $crawler->filter('[name="attachment[' . $attach_id . ']"]')->attr('disabled'));
+		$this->assertFalse($crawler->filter('[name="attachment[' . $attach_id . ']"]')->getNode(0)->hasAttribute('disabled'));
 	}
 
 	public function test_ucp_delete_expired_attachment()
@@ -219,7 +219,7 @@ class phpbb_functional_ucp_attachments_test extends phpbb_functional_test_case
 
 		$this->assertEquals('valid.jpg', $attachment_node->attr('title'));
 		$this->assertStringContainsString('download/attachment/' . $attach_id . '/valid.jpg', $attachment_node->attr('href'));
-		$this->assertEquals('disabled', $crawler->filter('[name="attachment[' . $attach_id . ']"]')->attr('disabled'));
+		$this->assertTrue($crawler->filter('[name="attachment[' . $attach_id . ']"]')->getNode(0)->hasAttribute('disabled'));
 
 		// It should not be possible to delete the attachment
 		$crawler = self::request('POST', 'ucp.php?i=ucp_attachments&mode=attachments&sid=' . $this->sid, [
@@ -238,7 +238,7 @@ class phpbb_functional_ucp_attachments_test extends phpbb_functional_test_case
 		});
 		$this->assertEquals('valid.jpg', $attachment_node->attr('title'));
 		$this->assertStringContainsString('download/attachment/' . $attach_id . '/valid.jpg', $attachment_node->attr('href'));
-		$this->assertEquals('disabled', $crawler->filter('[name="attachment[' . $attach_id . ']"]')->attr('disabled'));
+		$this->assertTrue($crawler->filter('[name="attachment[' . $attach_id . ']"]')->getNode(0)->hasAttribute('disabled'));
 
 		$this->logout();
 
@@ -327,7 +327,7 @@ class phpbb_functional_ucp_attachments_test extends phpbb_functional_test_case
 
 		$this->assertEquals('valid.jpg', $attachment_node->attr('title'));
 		$this->assertStringContainsString('download/attachment/' . $attach_id . '/valid.jpg', $attachment_node->attr('href'));
-		$this->assertEquals('', $crawler->filter('[name="attachment[' . $attach_id . ']"]')->attr('disabled'));
+		$this->assertFalse($crawler->filter('[name="attachment[' . $attach_id . ']"]')->getNode(0)->hasAttribute('disabled'));
 
 		// Update message time to 60 minutes later
 		$sql = 'UPDATE ' . PRIVMSGS_TABLE . '
@@ -347,7 +347,7 @@ class phpbb_functional_ucp_attachments_test extends phpbb_functional_test_case
 
 		$this->assertEquals('valid.jpg', $attachment_node->attr('title'));
 		$this->assertStringContainsString('download/attachment/' . $attach_id . '/valid.jpg', $attachment_node->attr('href'));
-		$this->assertEquals('disabled', $crawler->filter('[name="attachment[' . $attach_id . ']"]')->attr('disabled'));
+		$this->assertTrue($crawler->filter('[name="attachment[' . $attach_id . ']"]')->getNode(0)->hasAttribute('disabled'));
 
 		$this->set_flood_interval(15);
 
diff --git a/tests/mock/container_builder.php b/tests/mock/container_builder.php
index 29050825db..9200ed0767 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($id, $invalidBehavior = self::EXCEPTION_ON_INVALID_REFERENCE)
+	public function get(string $id, int $invalidBehavior = self::EXCEPTION_ON_INVALID_REFERENCE): ?object
 	{
 		if ($this->has($id))
 		{
@@ -79,11 +79,11 @@ class phpbb_mock_container_builder implements ContainerInterface
 	*
 	* @param string $id The service identifier
 	*
-	* @return Boolean true if the service is defined, false otherwise
+	* @return bool true if the service is defined, false otherwise
 	*
 	* @api
 	*/
-	public function has($id)
+	public function has(string $id): bool
 	{
 		return isset($this->services[$id]);
 	}
@@ -99,7 +99,7 @@ class phpbb_mock_container_builder implements ContainerInterface
 	*
 	* @api
 	*/
-	public function getParameter($name)
+	public function getParameter(string $name): mixed
 	{
 		if ($this->hasParameter($name))
 		{
@@ -114,11 +114,11 @@ class phpbb_mock_container_builder implements ContainerInterface
 	*
 	* @param string $name The parameter name
 	*
-	* @return Boolean The presence of parameter in container
+	* @return bool The presence of parameter in container
 	*
 	* @api
 	*/
-	public function hasParameter($name)
+	public function hasParameter(string $name): bool
 	{
 		return isset($this->parameters[$name]);
 	}
@@ -202,7 +202,7 @@ class phpbb_mock_container_builder implements ContainerInterface
 		return false;
 	}
 
-	public function initialized($id)
+	public function initialized($id): bool
 	{
 		return true;
 	}
diff --git a/tests/path_helper/path_helper_test.php b/tests/path_helper/path_helper_test.php
index 73d235e0cd..a2abefb108 100644
--- a/tests/path_helper/path_helper_test.php
+++ b/tests/path_helper/path_helper_test.php
@@ -127,8 +127,8 @@ class phpbb_path_helper_test extends phpbb_test_case
 			array(
 				$this->phpbb_root_path . 'test.php',
 				'/',
-				null,
-				null,
+				'',
+				'',
 				'',
 			),
 			array(