diff --git a/phpBB/phpbb/debug/error_handler.php b/phpBB/phpbb/debug/error_handler.php
index ebd828b97f..f2b00e6365 100644
--- a/phpBB/phpbb/debug/error_handler.php
+++ b/phpBB/phpbb/debug/error_handler.php
@@ -15,8 +15,14 @@ namespace phpbb\debug;
 
 use Symfony\Component\Debug\ErrorHandler;
 
+/**
+ * @psalm-suppress InvalidExtendClass
+ */
 class error_handler extends ErrorHandler
 {
+	/**
+	 * @psalm-suppress MethodSignatureMismatch
+	 */
 	public function handleError($type, $message, $file, $line)
 	{
 		if ($type === E_USER_WARNING || $type === E_USER_NOTICE)
diff --git a/phpBB/phpbb/event/md_exporter.php b/phpBB/phpbb/event/md_exporter.php
index 8ddc213020..5d2155369a 100644
--- a/phpBB/phpbb/event/md_exporter.php
+++ b/phpBB/phpbb/event/md_exporter.php
@@ -461,7 +461,7 @@ class md_exporter
 	* Validate "Changed" Information
 	*
 	* @param string $changed
-	* @return string
+	* @return array{string, string} Changed information containing version and description in respective order
 	* @throws \LogicException
 	*/
 	public function validate_changed($changed)
@@ -481,7 +481,7 @@ class md_exporter
 			throw new \LogicException("Invalid changed information found for event '{$this->current_event}'");
 		}
 
-		return array($version, $description);
+		return [$version, $description];
 	}
 
 	/**
@@ -492,7 +492,7 @@ class md_exporter
 	*/
 	public function validate_version($version)
 	{
-		return preg_match('#^\d+\.\d+\.\d+(?:-(?:a|b|RC|pl)\d+)?$#', $version);
+		return (bool) preg_match('#^\d+\.\d+\.\d+(?:-(?:a|b|RC|pl)\d+)?$#', $version);
 	}
 
 	/**
diff --git a/phpBB/phpbb/event/php_exporter.php b/phpBB/phpbb/event/php_exporter.php
index 720088d3d1..ba8ffbbe36 100644
--- a/phpBB/phpbb/event/php_exporter.php
+++ b/phpBB/phpbb/event/php_exporter.php
@@ -148,8 +148,9 @@ class php_exporter
 		$files = array();
 		foreach ($iterator as $file_info)
 		{
-			/** @var \RecursiveDirectoryIterator $file_info */
-			$relative_path = $iterator->getInnerIterator()->getSubPathname();
+			/** @var \RecursiveDirectoryIterator $inner_iterator */
+			$inner_iterator = $iterator->getInnerIterator();
+			$relative_path = $inner_iterator->getSubPathname();
 			$files[] = str_replace(DIRECTORY_SEPARATOR, '/', $relative_path);
 		}
 
diff --git a/phpBB/phpbb/event/recursive_event_filter_iterator.php b/phpBB/phpbb/event/recursive_event_filter_iterator.php
index 64e2e56f6a..22a6861522 100644
--- a/phpBB/phpbb/event/recursive_event_filter_iterator.php
+++ b/phpBB/phpbb/event/recursive_event_filter_iterator.php
@@ -41,7 +41,9 @@ class recursive_event_filter_iterator extends \RecursiveFilterIterator
 	*/
 	public function getChildren()
 	{
-		return new self($this->getInnerIterator()->getChildren(), $this->root_path);
+		$inner_iterator = $this->getInnerIterator();
+		assert($inner_iterator instanceof \RecursiveIterator);
+		return new self($inner_iterator->getChildren(), $this->root_path);
 	}
 
 	/**
diff --git a/phpBB/phpbb/extension/base.php b/phpBB/phpbb/extension/base.php
index 57a281fdae..c53d27efd1 100644
--- a/phpBB/phpbb/extension/base.php
+++ b/phpBB/phpbb/extension/base.php
@@ -35,7 +35,7 @@ class base implements \phpbb\extension\extension_interface
 	/** @var string */
 	protected $extension_path;
 
-	/** @var string[]|bool */
+	/** @var string[]|false */
 	private $migrations = false;
 
 	/**
@@ -69,7 +69,7 @@ class base implements \phpbb\extension\extension_interface
 	* Single enable step that installs any included migrations
 	*
 	* @param mixed $old_state State returned by previous call of this method
-	* @return false Indicates no further steps are required
+	* @return bool True if further steps are necessary, otherwise false
 	*/
 	public function enable_step($old_state)
 	{
@@ -95,7 +95,7 @@ class base implements \phpbb\extension\extension_interface
 	* Single purge step that reverts any included and installed migrations
 	*
 	* @param mixed $old_state State returned by previous call of this method
-	* @return false Indicates no further steps are required
+	* @return bool True if further steps are necessary, otherwise false
 	*/
 	public function purge_step($old_state)
 	{
@@ -135,8 +135,6 @@ class base implements \phpbb\extension\extension_interface
 
 		$this->migrator->set_migrations($migrations);
 
-		$migrations = $this->migrator->get_migrations();
-
-		return $migrations;
+		return $this->migrator->get_migrations();
 	}
 }
diff --git a/phpBB/phpbb/extension/manager.php b/phpBB/phpbb/extension/manager.php
index 0590adfc98..27257239f6 100644
--- a/phpBB/phpbb/extension/manager.php
+++ b/phpBB/phpbb/extension/manager.php
@@ -69,7 +69,7 @@ class manager
 	/**
 	* Loads all extension information from the database
 	*
-	* @return null
+	* @return void
 	*/
 	public function load_extensions()
 	{