diff --git a/docs/appendix/upgrade-notes/5.x-to-6.0.rst b/docs/appendix/upgrade-notes/5.x-to-6.0.rst
index 5bbed8eb69f..274cf4aea57 100644
--- a/docs/appendix/upgrade-notes/5.x-to-6.0.rst
+++ b/docs/appendix/upgrade-notes/5.x-to-6.0.rst
@@ -104,6 +104,8 @@ Removed lib functions
 * ``elgg_disable_annotations()`` has been removed
 * ``elgg_enable_annotations()`` has been removed
 * ``elgg_set_view_location()`` has been removed
+* ``elgg_strrchr()`` has been removed
+* ``elgg_strripos()`` has been removed
 * ``elgg_unrequire_css()`` has been removed. Use ``elgg_unregister_external_file('css', $view)`` as replacement.
 
 Removed class functions
diff --git a/engine/classes/Elgg/Cli.php b/engine/classes/Elgg/Cli.php
index 47afaf76d8e..b74e350efd6 100644
--- a/engine/classes/Elgg/Cli.php
+++ b/engine/classes/Elgg/Cli.php
@@ -22,21 +22,6 @@ class Cli {
 	 */
 	protected $console;
 
-	/**
-	 * @var EventsService
-	 */
-	protected $events;
-
-	/**
-	 * @var InputInterface
-	 */
-	protected $input;
-
-	/**
-	 * @var OutputInterface
-	 */
-	protected $output;
-
 	/**
 	 * Constructor
 	 *
@@ -45,18 +30,14 @@ class Cli {
 	 * @param OutputInterface $output Console output
 	 */
 	public function __construct(
-		EventsService $events,
-		InputInterface $input,
-		OutputInterface $output
+		protected EventsService $events,
+		protected InputInterface $input,
+		protected OutputInterface $output
 	) {
-		
 		$console = new \Elgg\Cli\Application('Elgg', elgg_get_release());
 		$console->setup($input, $output);
 
 		$this->console = $console;
-		$this->events = $events;
-		$this->input = $input;
-		$this->output = $output;
 	}
 
 	/**
@@ -64,7 +45,7 @@ public function __construct(
 	 *
 	 * @return void
 	 */
-	protected function bootstrap() {
+	protected function bootstrap(): void {
 		$commands = array_merge($this->getCoreCommands(), $this->getPluginCommands());
 		$commands = $this->events->triggerResults('commands', 'cli', [], $commands);
 
@@ -78,7 +59,7 @@ protected function bootstrap() {
 	 *
 	 * @return array
 	 */
-	protected function getCoreCommands() {
+	protected function getCoreCommands(): array {
 		$conf = \Elgg\Project\Paths::elgg() . 'engine/cli_commands.php';
 		return \Elgg\Includer::includeFile($conf);
 	}
@@ -88,7 +69,7 @@ protected function getCoreCommands() {
 	 *
 	 * @return array
 	 */
-	protected function getPluginCommands() {
+	protected function getPluginCommands(): array {
 		$return = [];
 		
 		$plugins = elgg_get_plugins('active');
@@ -112,7 +93,7 @@ protected function getPluginCommands() {
 	 *
 	 * @return void
 	 */
-	public function add($command) {
+	public function add(string $command): void {
 		if (!class_exists($command)) {
 			return;
 		}
@@ -150,7 +131,7 @@ public function add($command) {
 	 *
 	 * @return void
 	 */
-	public function run(bool $bootstrap = true) {
+	public function run(bool $bootstrap = true): void {
 		if ($bootstrap) {
 			$this->bootstrap();
 		}
@@ -163,7 +144,7 @@ public function run(bool $bootstrap = true) {
 	 *
 	 * @return InputInterface
 	 */
-	public function getInput() {
+	public function getInput(): InputInterface {
 		return $this->input;
 	}
 
@@ -172,7 +153,7 @@ public function getInput() {
 	 *
 	 * @return OutputInterface
 	 */
-	public function getOutput() {
+	public function getOutput(): OutputInterface {
 		return $this->output;
 	}
 }
diff --git a/engine/classes/Elgg/EmailService.php b/engine/classes/Elgg/EmailService.php
index 0d2f26aee46..ab1cf831e07 100644
--- a/engine/classes/Elgg/EmailService.php
+++ b/engine/classes/Elgg/EmailService.php
@@ -28,41 +28,6 @@ class EmailService {
 
 	use Loggable;
 
-	/**
-	 * @var Config
-	 */
-	protected $config;
-
-	/**
-	 * @var EventsService
-	 */
-	protected $events;
-
-	/**
-	 * @var TransportInterface
-	 */
-	protected $mailer;
-
-	/**
-	 * @var HtmlFormatter
-	 */
-	protected $html_formatter;
-
-	/**
-	 * @var ImageFetcherService
-	 */
-	protected $image_fetcher;
-
-	/**
-	 * @var ViewsService
-	 */
-	protected $views;
-
-	/**
-	 * @var CssCompiler
-	 */
-	protected $css_compiler;
-
 	/**
 	 * Constructor
 	 *
@@ -75,21 +40,14 @@ class EmailService {
 	 * @param CssCompiler         $css_compiler   Css compiler
 	 */
 	public function __construct(
-			Config $config,
-			EventsService $events,
-			TransportInterface $mailer,
-			HtmlFormatter $html_formatter,
-			ViewsService $views,
-			ImageFetcherService $image_fetcher,
-			CssCompiler $css_compiler
-		) {
-		$this->config = $config;
-		$this->events = $events;
-		$this->mailer = $mailer;
-		$this->html_formatter = $html_formatter;
-		$this->views = $views;
-		$this->image_fetcher = $image_fetcher;
-		$this->css_compiler = $css_compiler;
+		protected Config $config,
+		protected EventsService $events,
+		protected TransportInterface $mailer,
+		protected HtmlFormatter $html_formatter,
+		protected ViewsService $views,
+		protected ImageFetcherService $image_fetcher,
+		protected CssCompiler $css_compiler
+	) {
 	}
 
 	/**
@@ -100,7 +58,7 @@ public function __construct(
 	 * @return bool
 	 * @throws RuntimeException
 	 */
-	public function send(Email $email) {
+	public function send(Email $email): bool {
 		$email = $this->events->triggerResults('prepare', 'system:email', [], $email);
 		if (!$email instanceof Email) {
 			$msg = "'prepare','system:email' event handlers should return an instance of " . Email::class;
@@ -123,8 +81,7 @@ public function send(Email $email) {
 	 * @return bool
 	 * @throws RuntimeException
 	 */
-	public function transport(Email $email) {
-
+	public function transport(Email $email): bool {
 		if ($this->events->triggerResults('transport', 'system:email', ['email' => $email], false)) {
 			return true;
 		}
diff --git a/engine/classes/Elgg/Event.php b/engine/classes/Elgg/Event.php
index 262e37cc8ac..b82c7fbb80a 100644
--- a/engine/classes/Elgg/Event.php
+++ b/engine/classes/Elgg/Event.php
@@ -10,31 +10,6 @@
  */
 class Event {
 	
-	/**
-	 * @var PublicContainer
-	 */
-	protected $dic;
-	
-	/**
-	 * @var string
-	 */
-	protected $name;
-	
-	/**
-	 * @var string
-	 */
-	protected $type;
-	
-	/**
-	 * @var mixed
-	 */
-	protected $value;
-	
-	/**
-	 * @var mixed
-	 */
-	protected $params;
-	
 	/**
 	 * Constructor
 	 *
@@ -44,12 +19,13 @@ class Event {
 	 * @param mixed           $value  Event value
 	 * @param mixed           $params Event params
 	 */
-	public function __construct(PublicContainer $dic, string $name, string $type, $value = null, $params = []) {
-		$this->dic = $dic;
-		$this->name = $name;
-		$this->type = $type;
-		$this->value = $value;
-		$this->params = $params;
+	public function __construct(
+		protected PublicContainer $dic,
+		protected string $name,
+		protected string $type,
+		protected $value = null,
+		protected $params = []
+	) {
 	}
 	
 	/**
diff --git a/engine/classes/Elgg/Filesystem/File.php b/engine/classes/Elgg/Filesystem/File.php
index 808b2940e14..5f759ed6de4 100644
--- a/engine/classes/Elgg/Filesystem/File.php
+++ b/engine/classes/Elgg/Filesystem/File.php
@@ -10,34 +10,26 @@
  */
 class File {
 	
-	/** @var Directory */
-	private $directory;
-	
-	/** @var string */
-	private $path;
-	
 	/**
 	 * Constructor
 	 *
 	 * @param Directory $directory The directory where this file resides
 	 * @param string    $path      The path to this file relative to the directory
 	 */
-	public function __construct(Directory $directory, $path) {
-		$this->directory = $directory;
-		$this->path = $path;
+	public function __construct(protected Directory $directory, protected string $path) {
 	}
 	
 	/**
 	 * @return boolean Whether this file exists.
 	 */
-	public function exists() {
+	public function exists(): bool {
 		return $this->directory->isFile($this->path);
 	}
 	
 	/**
 	 * @return string The file's basename.
 	 */
-	public function getBasename() {
+	public function getBasename(): string {
 		return pathinfo($this->path, PATHINFO_BASENAME);
 	}
 	
@@ -46,7 +38,7 @@ public function getBasename() {
 	 *
 	 * @return string
 	 */
-	public function getContents() {
+	public function getContents(): string {
 		return $this->directory->getContents($this->path);
 	}
 
@@ -56,21 +48,21 @@ public function getContents() {
 	 * @param string $content File content
 	 * @return void
 	 */
-	public function putContents($content) {
+	public function putContents($content): void {
 		$this->directory->putContents($this->path, $content);
 	}
 	
 	/**
 	 * @return string The file's extension.
 	 */
-	public function getExtension() {
+	public function getExtension(): string {
 		return pathinfo($this->path, PATHINFO_EXTENSION);
 	}
 	
 	/**
 	 * @return string The full path to this file.
 	 */
-	public function getPath() {
+	public function getPath(): string {
 		return $this->directory->getPath($this->path);
 	}
 	
diff --git a/engine/classes/Elgg/Forms/StickyForms.php b/engine/classes/Elgg/Forms/StickyForms.php
index 8fbd65b0149..47775453c16 100644
--- a/engine/classes/Elgg/Forms/StickyForms.php
+++ b/engine/classes/Elgg/Forms/StickyForms.php
@@ -9,19 +9,13 @@
  * @internal
  */
 class StickyForms {
-	
-	/**
-	 * @var \ElggSession
-	 */
-	protected $session;
-	
+
 	/**
 	 * Constructor
 	 *
 	 * @param \ElggSession $session Session for storage
 	 */
-	public function __construct(\ElggSession $session) {
-		$this->session = $session;
+	public function __construct(protected \ElggSession $session) {
 	}
 	
 	/**
diff --git a/engine/classes/Elgg/Gatekeeper.php b/engine/classes/Elgg/Gatekeeper.php
index bc77209eaa9..23040aebc3e 100644
--- a/engine/classes/Elgg/Gatekeeper.php
+++ b/engine/classes/Elgg/Gatekeeper.php
@@ -23,36 +23,6 @@
  */
 class Gatekeeper {
 
-	/**
-	 * @var SessionManagerService
-	 */
-	protected $session_manager;
-
-	/**
-	 * @var \Elgg\Http\Request
-	 */
-	protected $request;
-
-	/**
-	 * @var RedirectService
-	 */
-	protected $redirects;
-
-	/**
-	 * @var EntityTable
-	 */
-	protected $entities;
-
-	/**
-	 * @var AccessCollections
-	 */
-	protected $access;
-
-	/**
-	 * @var Translator
-	 */
-	protected $translator;
-
 	/**
 	 * Constructor
 	 *
@@ -64,27 +34,22 @@ class Gatekeeper {
 	 * @param Translator            $translator      Translator
 	 */
 	public function __construct(
-		SessionManagerService $session_manager,
-		HttpRequest $request,
-		RedirectService $redirects,
-		EntityTable $entities,
-		AccessCollections $access,
-		Translator $translator
+		protected SessionManagerService $session_manager,
+		protected HttpRequest $request,
+		protected RedirectService $redirects,
+		protected EntityTable $entities,
+		protected AccessCollections $access,
+		protected Translator $translator
 	) {
-		$this->session_manager = $session_manager;
-		$this->request = $request;
-		$this->redirects = $redirects;
-		$this->entities = $entities;
-		$this->access = $access;
-		$this->translator = $translator;
 	}
 
 	/**
 	 * Require a user to be authenticated to with code execution
+	 *
 	 * @return void
 	 * @throws LoggedInGatekeeperException
 	 */
-	public function assertAuthenticatedUser() {
+	public function assertAuthenticatedUser(): void {
 		if ($this->session_manager->isLoggedIn()) {
 			return;
 		}
@@ -96,10 +61,11 @@ public function assertAuthenticatedUser() {
 
 	/**
 	 * Require a user to be not authenticated (logged out) to with code execution
+	 *
 	 * @return void
 	 * @throws LoggedOutGatekeeperException
 	 */
-	public function assertUnauthenticatedUser() {
+	public function assertUnauthenticatedUser(): void {
 		if (!$this->session_manager->isLoggedIn()) {
 			return;
 		}
@@ -112,11 +78,12 @@ public function assertUnauthenticatedUser() {
 
 	/**
 	 * Require an admin user to be authenticated to proceed with code execution
+	 *
 	 * @return void
 	 * @throws GatekeeperException
 	 * @throws AdminGatekeeperException
 	 */
-	public function assertAuthenticatedAdmin() {
+	public function assertAuthenticatedAdmin(): void {
 		$this->assertAuthenticatedUser();
 
 		$user = $this->session_manager->getLoggedInUser();
@@ -307,7 +274,7 @@ public function assertAccessibleGroup(\ElggGroup $group, \ElggUser $user = null)
 	 * @return void
 	 * @throws AjaxGatekeeperException
 	 */
-	public function assertXmlHttpRequest() {
+	public function assertXmlHttpRequest(): void {
 		if ($this->request->isXmlHttpRequest()) {
 			return;
 		}
diff --git a/engine/classes/Elgg/Groups/Tool.php b/engine/classes/Elgg/Groups/Tool.php
index cacd7608979..731fe8dab5a 100644
--- a/engine/classes/Elgg/Groups/Tool.php
+++ b/engine/classes/Elgg/Groups/Tool.php
@@ -14,15 +14,7 @@
  */
 class Tool implements CollectionItemInterface {
 
-	/**
-	 * @var string
-	 */
-	public $name;
-
-	/**
-	 * @var array
-	 */
-	protected $options;
+	protected array $options;
 
 	/**
 	 * Constructor
@@ -30,9 +22,7 @@ class Tool implements CollectionItemInterface {
 	 * @param string $name    Tool name
 	 * @param array  $options Tool options
 	 */
-	public function __construct($name, array $options = []) {
-		$this->name = $name;
-
+	public function __construct(public string $name, array $options = []) {
 		$defaults = [
 			'label' => null,
 			'default_on' => true,
@@ -83,7 +73,7 @@ public function getPriority() {
 	 *
 	 * @return string
 	 */
-	public function getLabel() {
+	public function getLabel(): string {
 		$label = elgg_extract('label', $this->options);
 		if (isset($label)) {
 			return $label;
@@ -108,9 +98,10 @@ public function getDescription(): ?string {
 
 	/**
 	 * Is the tool enabled by default?
+	 *
 	 * @return bool
 	 */
-	public function isEnabledByDefault() {
+	public function isEnabledByDefault(): bool {
 		$default_on = elgg_extract('default_on', $this->options, true);
 
 		if ($default_on === true || $default_on === 'yes') {
@@ -122,9 +113,10 @@ public function isEnabledByDefault() {
 
 	/**
 	 * Get metadata name for DB storage
+	 *
 	 * @return string
 	 */
-	public function mapMetadataName() {
+	public function mapMetadataName(): string {
 		return "{$this->name}_enable";
 	}
 
@@ -136,7 +128,7 @@ public function mapMetadataName() {
 	 *
 	 * @return string
 	 */
-	public function mapMetadataValue($value = null) {
+	public function mapMetadataValue($value = null): string {
 		if (!isset($value)) {
 			$value = $this->default_on;
 		}
diff --git a/engine/classes/Elgg/Http/WebAppManifestResource.php b/engine/classes/Elgg/Http/WebAppManifestResource.php
index ea59c15e755..d42d52dd1a4 100644
--- a/engine/classes/Elgg/Http/WebAppManifestResource.php
+++ b/engine/classes/Elgg/Http/WebAppManifestResource.php
@@ -13,17 +13,13 @@
  * @internal
  */
 class WebAppManifestResource {
-	
-	/** @var \ElggSite */
-	private $site;
-	
+
 	/**
 	 * Constructor
 	 *
 	 * @param \ElggSite $site The site serving this manifest.
 	 */
-	public function __construct(\ElggSite $site) {
-		$this->site = $site;
+	public function __construct(protected \ElggSite $site) {
 	}
 	
 	/**
@@ -31,7 +27,7 @@ public function __construct(\ElggSite $site) {
 	 *
 	 * @return array
 	 */
-	public function get() {
+	public function get(): array {
 		return [
 			'display' => 'standalone',
 			'name' => $this->site->getDisplayName(),
diff --git a/engine/classes/Elgg/I18n/Locale.php b/engine/classes/Elgg/I18n/Locale.php
index 508abb001b9..fe57fa563e0 100644
--- a/engine/classes/Elgg/I18n/Locale.php
+++ b/engine/classes/Elgg/I18n/Locale.php
@@ -11,17 +11,13 @@
  * @internal
  */
 final class Locale {
-	
-	/** @var string */
-	private $locale;
-	
+
 	/**
 	 * Use Locale::parse to construct
 	 *
 	 * @param string $locale A string representation of the locale
 	 */
-	private function __construct($locale) {
-		$this->locale = $locale;
+	private function __construct(private string $locale) {
 	}
 	
 	/**
@@ -40,9 +36,9 @@ public function __toString() {
 	 *
 	 * @throws InvalidLocaleException
 	 */
-	public static function parse($locale) {
+	public static function parse(string $locale): Locale {
 		if (!preg_match('~^[a-z0-9_]{2,20}$~', $locale)) {
-			throw new InvalidLocaleException("Unrecognized locale: $locale");
+			throw new InvalidLocaleException("Unrecognized locale: {$locale}");
 		}
 		
 		return new Locale($locale);
diff --git a/engine/classes/Elgg/PersistentLoginService.php b/engine/classes/Elgg/PersistentLoginService.php
index cb248fb7a0a..834cfb270d5 100644
--- a/engine/classes/Elgg/PersistentLoginService.php
+++ b/engine/classes/Elgg/PersistentLoginService.php
@@ -18,30 +18,9 @@ class PersistentLoginService {
 	
 	use TimeUsing;
 	
-	/**
-	 * @var array
-	 */
-	protected $cookie_config;
-	
-	/**
-	 * @var string
-	 */
-	protected $cookie_token;
-	
-	/**
-	 * @var \ElggSession
-	 */
-	protected $session;
+	protected array $cookie_config;
 	
-	/**
-	 * @var \Elgg\Security\Crypto
-	 */
-	protected $crypto;
-	
-	/**
-	 * @var UsersRememberMeCookiesTable
-	 */
-	protected $persistent_cookie_table;
+	protected string $cookie_token;
 	
 	/**
 	 * @var callable
@@ -59,15 +38,12 @@ class PersistentLoginService {
 	 * @param \Elgg\Http\Request          $request      The request
 	 */
 	public function __construct(
-			UsersRememberMeCookiesTable $cookie_table,
-			\ElggSession $session,
-			\Elgg\Security\Crypto $crypto,
-			\Elgg\Config $config,
-			\Elgg\Http\Request $request) {
-		$this->persistent_cookie_table = $cookie_table;
-		$this->session = $session;
-		$this->crypto = $crypto;
-		
+		protected UsersRememberMeCookiesTable $cookie_table,
+		protected \ElggSession $session,
+		protected \Elgg\Security\Crypto $crypto,
+		\Elgg\Config $config,
+		\Elgg\Http\Request $request
+	) {
 		$global_cookies_config = $config->getCookieConfig();
 		
 		$this->cookie_config = $global_cookies_config['remember_me'];
@@ -85,7 +61,7 @@ public function makeLoginPersistent(\ElggUser $user): void {
 		$token = $this->generateToken();
 		$hash = $this->hashToken($token);
 
-		$this->persistent_cookie_table->insertHash($user, $hash);
+		$this->cookie_table->insertHash($user, $hash);
 		$this->setCookie($token);
 		$this->setSessionToken($token);
 	}
@@ -98,7 +74,7 @@ public function makeLoginPersistent(\ElggUser $user): void {
 	public function removePersistentLogin(): void {
 		if ($this->cookie_token) {
 			$client_hash = $this->hashToken($this->cookie_token);
-			$this->persistent_cookie_table->deleteHash($client_hash);
+			$this->cookie_table->deleteHash($client_hash);
 		}
 
 		$this->setCookie('');
@@ -114,7 +90,7 @@ public function removePersistentLogin(): void {
 	 * @return void
 	 */
 	public function handlePasswordChange(\ElggUser $subject, \ElggUser $modifier = null): void {
-		$this->persistent_cookie_table->deleteAllHashes($subject);
+		$this->cookie_table->deleteAllHashes($subject);
 		if (!$modifier || ($modifier->guid !== $subject->guid) || !$this->cookie_token) {
 			return;
 		}
@@ -162,7 +138,7 @@ public function getUserFromToken(string $token): ?\ElggUser {
 			return null;
 		}
 		
-		$user_row = $this->persistent_cookie_table->getRowFromHash($hash);
+		$user_row = $this->cookie_table->getRowFromHash($hash);
 		if (empty($user_row)) {
 			return null;
 		}
@@ -185,7 +161,7 @@ public function updateTokenUsage(\ElggUser $user): ?bool {
 		
 		// update the database record
 		// not interested in number of updated rows, as an update in the same second won't update the row
-		$this->persistent_cookie_table->updateHash($user, $this->hashToken($this->cookie_token));
+		$this->cookie_table->updateHash($user, $this->hashToken($this->cookie_token));
 		
 		// also update the cookie lifetime client-side
 		$this->setCookie($this->cookie_token);
@@ -211,7 +187,7 @@ public function removeExpiredTokens($time): bool {
 			return false;
 		}
 		
-		return (bool) $this->persistent_cookie_table->deleteExpiredHashes($time->getTimestamp());
+		return (bool) $this->cookie_table->deleteExpiredHashes($time->getTimestamp());
 	}
 
 	/**
diff --git a/engine/classes/Elgg/Plugin/Composer.php b/engine/classes/Elgg/Plugin/Composer.php
index 7a37daeb78c..04cf1b5abe6 100644
--- a/engine/classes/Elgg/Plugin/Composer.php
+++ b/engine/classes/Elgg/Plugin/Composer.php
@@ -16,11 +16,6 @@
  */
 class Composer {
 	
-	/**
-	 * @var \ElggPlugin
-	 */
-	protected $plugin;
-	
 	/**
 	 * @var \Eloquent\Composer\Configuration\Element\Configuration
 	 */
@@ -33,9 +28,7 @@ class Composer {
 	 *
 	 * @throws ComposerException
 	 */
-	public function __construct(\ElggPlugin $plugin) {
-		$this->plugin = $plugin;
-		
+	public function __construct(protected \ElggPlugin $plugin) {
 		try {
 			// need to suppress warning because of deprecated notices that get converted to warnings during phpunit
 			$reader = @new \Eloquent\Composer\Configuration\ConfigurationReader;
diff --git a/engine/classes/Elgg/Router.php b/engine/classes/Elgg/Router.php
index be79b48b9ab..ff2eee22c94 100644
--- a/engine/classes/Elgg/Router.php
+++ b/engine/classes/Elgg/Router.php
@@ -27,36 +27,6 @@ class Router {
 
 	use Profilable;
 
-	/**
-	 * @var EventsService
-	 */
-	protected $events;
-
-	/**
-	 * @var RouteCollection
-	 */
-	protected $routes;
-
-	/**
-	 * @var UrlMatcher
-	 */
-	protected $matcher;
-
-	/**
-	 * @var HandlersService
-	 */
-	protected $handlers;
-
-	/**
-	 * @var ResponseFactory
-	 */
-	protected $response;
-
-	/**
-	 * @var Plugins
-	 */
-	protected $plugins;
-
 	/**
 	 * Constructor
 	 *
@@ -68,19 +38,13 @@ class Router {
 	 * @param Plugins         $plugins  Plugins
 	 */
 	public function __construct(
-		EventsService $events,
-		RouteCollection $routes,
-		UrlMatcher $matcher,
-		HandlersService $handlers,
-		ResponseFactory $response,
-		Plugins $plugins
+		protected EventsService $events,
+		protected RouteCollection $routes,
+		protected UrlMatcher $matcher,
+		protected HandlersService $handlers,
+		protected ResponseFactory $response,
+		protected Plugins $plugins
 	) {
-		$this->events = $events;
-		$this->routes = $routes;
-		$this->matcher = $matcher;
-		$this->handlers = $handlers;
-		$this->response = $response;
-		$this->plugins = $plugins;
 	}
 
 	/**
@@ -93,7 +57,7 @@ public function __construct(
 	 *
 	 * @return boolean Whether the request was routed successfully.
 	 */
-	public function route(HttpRequest $request) {
+	public function route(HttpRequest $request): bool {
 		$this->beginTimer(['build page']);
 
 		$request->validate();
diff --git a/engine/classes/Elgg/Security/Hmac.php b/engine/classes/Elgg/Security/Hmac.php
index 8a6886bd979..3f661e0d467 100644
--- a/engine/classes/Elgg/Security/Hmac.php
+++ b/engine/classes/Elgg/Security/Hmac.php
@@ -9,25 +9,12 @@
  */
 class Hmac {
 
-	/**
-	 * @var string
-	 */
-	private $key;
-
 	/**
 	 * @var callable
 	 */
-	private $comparator;
+	protected $comparator;
 
-	/**
-	 * @var string
-	 */
-	private $data;
-
-	/**
-	 * @var string
-	 */
-	private $algo;
+	protected string $data;
 
 	/**
 	 * Constructor
@@ -39,8 +26,7 @@ class Hmac {
 	 *
 	 * @throws \Elgg\Exceptions\InvalidArgumentException
 	 */
-	public function __construct($key, callable $comparator, $data, $algo = 'sha256') {
-		$this->key = $key;
+	public function __construct(protected string $key, callable $comparator, $data, protected string $algo = 'sha256') {
 		$this->comparator = $comparator;
 		if (!$data) {
 			throw new InvalidArgumentException('$data cannot be empty');
@@ -51,7 +37,6 @@ public function __construct($key, callable $comparator, $data, $algo = 'sha256')
 		}
 		
 		$this->data = $data;
-		$this->algo = $algo;
 	}
 
 	/**
@@ -59,7 +44,7 @@ public function __construct($key, callable $comparator, $data, $algo = 'sha256')
 	 *
 	 * @return string
 	 */
-	public function getToken() {
+	public function getToken(): string {
 		$bytes = hash_hmac($this->algo, $this->data, $this->key, true);
 		return Base64Url::encode($bytes);
 	}
@@ -68,9 +53,10 @@ public function getToken() {
 	 * Does the MAC match the given token?
 	 *
 	 * @param string $token HMAC token in Base64URL encoding
+	 *
 	 * @return bool
 	 */
-	public function matchesToken($token) {
+	public function matchesToken($token): bool {
 		$expected_token = $this->getToken();
 		return call_user_func($this->comparator, $expected_token, $token);
 	}
diff --git a/engine/classes/Elgg/SessionManagerService.php b/engine/classes/Elgg/SessionManagerService.php
index b37ee014c20..f9fe957b232 100644
--- a/engine/classes/Elgg/SessionManagerService.php
+++ b/engine/classes/Elgg/SessionManagerService.php
@@ -14,51 +14,12 @@
  * @since 5.0
  */
 class SessionManagerService {
-
-	/**
-	 * @var EntityCache
-	 */
-	protected $entity_cache;
-	
-	/**
-	 * @var EventsService
-	 */
-	protected $events;
-	
-	/**
-	 * @var bool
-	 */
-	protected $ignore_access = false;
-	
-	/**
-	 * @var \ElggUser|null
-	 */
-	protected $logged_in_user;
 	
-	/**
-	 * @var PersistentLoginService
-	 */
-	protected $persistent_login;
-	
-	/**
-	 * @var bool
-	 */
-	protected $show_disabled_entities = false;
-	
-	/**
-	 * @var \ElggSession
-	 */
-	protected $session;
+	protected bool $ignore_access = false;
 	
-	/**
-	 * @var SessionCache
-	 */
-	protected $session_cache;
+	protected ?\ElggUser $logged_in_user = null;
 	
-	/**
-	 * @var Translator
-	 */
-	protected $translator;
+	protected bool $show_disabled_entities = false;
 	
 	/**
 	 * Constructor
@@ -71,19 +32,13 @@ class SessionManagerService {
 	 * @param EntityCache            $entity_cache     the entity cache
 	 */
 	public function __construct(
-		\ElggSession $session,
-		EventsService $events,
-		Translator $translator,
-		PersistentLoginService $persistent_login,
-		SessionCache $session_cache,
-		EntityCache $entity_cache
-		) {
-		$this->session = $session;
-		$this->events = $events;
-		$this->translator = $translator;
-		$this->persistent_login = $persistent_login;
-		$this->session_cache = $session_cache;
-		$this->entity_cache = $entity_cache;
+		protected \ElggSession $session,
+		protected EventsService $events,
+		protected Translator $translator,
+		protected PersistentLoginService $persistent_login,
+		protected SessionCache $session_cache,
+		protected EntityCache $entity_cache
+	) {
 	}
 	
 	/**
diff --git a/engine/classes/Elgg/Structs/Collection/InMemory.php b/engine/classes/Elgg/Structs/Collection/InMemory.php
index d40363235bc..44bdc105e62 100644
--- a/engine/classes/Elgg/Structs/Collection/InMemory.php
+++ b/engine/classes/Elgg/Structs/Collection/InMemory.php
@@ -12,16 +12,12 @@
  */
 final class InMemory implements Collection {
 	
-	/** @var array */
-	private $items;
-	
 	/**
 	 * Constructor
 	 *
 	 * @param array $items The set of items in the collection
 	 */
-	private function __construct(array $items = []) {
-		$this->items = $items;
+	private function __construct(protected array $items = []) {
 	}
 	
 	/**
diff --git a/engine/classes/Elgg/Upgrade/Batch.php b/engine/classes/Elgg/Upgrade/Batch.php
index 0e373433e9a..f4333580766 100644
--- a/engine/classes/Elgg/Upgrade/Batch.php
+++ b/engine/classes/Elgg/Upgrade/Batch.php
@@ -14,18 +14,12 @@ abstract class Batch {
 	 */
 	const UNKNOWN_COUNT = -1;
 
-	/**
-	 * @var \ElggUpgrade
-	 */
-	protected $upgrade;
-
 	/**
 	 * Constructs a upgrade batch
 	 *
 	 * @param \ElggUpgrade $upgrade the upgrade related to this batch
 	 */
-	public function __construct(\ElggUpgrade $upgrade = null) {
-		$this->upgrade = $upgrade;
+	public function __construct(protected ?\ElggUpgrade $upgrade = null) {
 	}
 	
 	/**
diff --git a/engine/classes/Elgg/Upgrade/Loop.php b/engine/classes/Elgg/Upgrade/Loop.php
index 87352d356f5..1ae489fe672 100644
--- a/engine/classes/Elgg/Upgrade/Loop.php
+++ b/engine/classes/Elgg/Upgrade/Loop.php
@@ -16,45 +16,18 @@ class Loop {
 
 	use Loggable;
 
-	/**
-	 * @var \ElggUpgrade
-	 */
-	protected $upgrade;
-
-	/**
-	 * @var Result
-	 */
-	protected $result;
-
 	/**
 	 * @var Batch|false
 	 */
 	protected $batch;
 
-	/**
-	 * @var int
-	 */
-	protected $max_duration;
-
-	/**
-	 * @var int
-	 */
-	protected $count;
+	protected int $max_duration;
 
-	/**
-	 * @var int
-	 */
-	protected $processed;
+	protected int $count;
 
-	/**
-	 * @var int
-	 */
-	protected $offset;
+	protected int $processed;
 
-	/**
-	 * @var Progress
-	 */
-	protected $progress;
+	protected int $offset;
 
 	/**
 	 * Constructor
@@ -67,13 +40,13 @@ class Loop {
 	 * @throws RuntimeException
 	 */
 	public function __construct(
-		\ElggUpgrade $upgrade,
-		Result $result,
-		Progress $progress,
+		protected \ElggUpgrade $upgrade,
+		protected Result $result,
+		protected Progress $progress,
 		Logger $logger
 	) {
-		$this->upgrade = $upgrade;
-
+		$this->setLogger($logger);
+		
 		// Get the class taking care of the actual upgrading
 		$this->batch = $upgrade->getBatch();
 		if (!$this->batch) {
@@ -83,10 +56,6 @@ public function __construct(
 			]));
 		}
 
-		$this->result = $result;
-		$this->progress = $progress;
-		$this->logger = $logger;
-
 		$this->count = $this->batch->countItems();
 		$this->processed = (int) $upgrade->processed;
 		$this->offset = (int) $upgrade->offset;
diff --git a/engine/classes/Elgg/UpgradeService.php b/engine/classes/Elgg/UpgradeService.php
index 7ef90e9c1da..73283133ad4 100644
--- a/engine/classes/Elgg/UpgradeService.php
+++ b/engine/classes/Elgg/UpgradeService.php
@@ -23,41 +23,6 @@ class UpgradeService {
 
 	use Loggable;
 
-	/**
-	 * @var Locator
-	 */
-	protected $locator;
-
-	/**
-	 * @var Translator
-	 */
-	private $translator;
-
-	/**
-	 * @var EventsService
-	 */
-	private $events;
-
-	/**
-	 * @var Config
-	 */
-	private $config;
-
-	/**
-	 * @var Mutex
-	 */
-	private $mutex;
-
-	/**
-	 * @var SystemMessagesService
-	 */
-	private $system_messages;
-
-	/**
-	 * @var Progress
-	 */
-	protected $progress;
-
 	/**
 	 * Constructor
 	 *
@@ -70,28 +35,22 @@ class UpgradeService {
 	 * @param Progress              $progress        Progress
 	 */
 	public function __construct(
-		Locator $locator,
-		Translator $translator,
-		EventsService $events,
-		Config $config,
-		Mutex $mutex,
-		SystemMessagesService $system_messages,
-		Progress $progress
+		protected Locator $locator,
+		protected Translator $translator,
+		protected EventsService $events,
+		protected Config $config,
+		protected Mutex $mutex,
+		protected SystemMessagesService $system_messages,
+		protected Progress $progress
 	) {
-		$this->locator = $locator;
-		$this->translator = $translator;
-		$this->events = $events;
-		$this->config = $config;
-		$this->mutex = $mutex;
-		$this->system_messages = $system_messages;
-		$this->progress = $progress;
 	}
 
 	/**
 	 * Start an upgrade process
+	 *
 	 * @return Promise
 	 */
-	protected function up() {
+	protected function up(): Promise {
 		return new Promise(function ($resolve, $reject) {
 			Application::migrate();
 
@@ -114,9 +73,10 @@ protected function up() {
 
 	/**
 	 * Finish an upgrade process
+	 *
 	 * @return Promise
 	 */
-	protected function down() {
+	protected function down(): Promise {
 		return new Promise(function ($resolve, $reject) {
 			if (!$this->events->trigger('upgrade', 'system', null)) {
 				return $reject();
@@ -139,7 +99,7 @@ protected function down() {
 	 *
 	 * @return Promise
 	 */
-	protected function runUpgrades($upgrades) {
+	protected function runUpgrades($upgrades): Promise {
 		$promises = [];
 
 		foreach ($upgrades as $upgrade) {
@@ -176,7 +136,7 @@ protected function runUpgrades($upgrades) {
 	 *
 	 * @return Promise
 	 */
-	public function run($upgrades = null) {
+	public function run($upgrades = null): Promise {
 		// turn off time limit
 		set_time_limit(3600);
 
@@ -225,7 +185,7 @@ function ($result) use ($resolve) {
 	 *
 	 * @return \ElggUpgrade[]
 	 */
-	public function getPendingUpgrades($async = true) {
+	public function getPendingUpgrades(bool $async = true): array {
 		$pending = [];
 
 		$upgrades = $this->locator->locate();
@@ -259,7 +219,7 @@ public function getPendingUpgrades($async = true) {
 	 *
 	 * @return \ElggUpgrade[]
 	 */
-	public function getCompletedUpgrades($async = true) {
+	public function getCompletedUpgrades(bool $async = true): array {
 		// make sure always to return all upgrade entities
 		return elgg_call(
 			ELGG_IGNORE_ACCESS | ELGG_SHOW_DISABLED_ENTITIES,
@@ -312,7 +272,7 @@ function () use ($async) {
 	 *
 	 * @return Result
 	 */
-	public function executeUpgrade(\ElggUpgrade $upgrade, $max_duration = null) {
+	public function executeUpgrade(\ElggUpgrade $upgrade, int $max_duration = null): Result {
 		// Upgrade also disabled data, so the compatibility is
 		// preserved in case the data ever gets enabled again
 		return elgg_call(
diff --git a/engine/classes/Elgg/Users/Accounts.php b/engine/classes/Elgg/Users/Accounts.php
index aabd9f8f257..ec2b9f1adb5 100644
--- a/engine/classes/Elgg/Users/Accounts.php
+++ b/engine/classes/Elgg/Users/Accounts.php
@@ -19,36 +19,6 @@
  */
 class Accounts {
 
-	/**
-	 * @var Config
-	 */
-	protected $config;
-
-	/**
-	 * @var Translator
-	 */
-	protected $translator;
-
-	/**
-	 * @var PasswordService
-	 */
-	protected $passwords;
-
-	/**
-	 * @var EventsService
-	 */
-	protected $events;
-	
-	/**
-	 * @var EmailService
-	 */
-	protected $email;
-	
-	/**
-	 * @var PasswordGeneratorService
-	 */
-	protected $password_generator;
-
 	/**
 	 * Constructor
 	 *
@@ -60,19 +30,13 @@ class Accounts {
 	 * @param PasswordGeneratorService $password_generator Password generator service
 	 */
 	public function __construct(
-		Config $config,
-		Translator $translator,
-		PasswordService $passwords,
-		EventsService $events,
-		EmailService $email,
-		PasswordGeneratorService $password_generator
+		protected Config $config,
+		protected Translator $translator,
+		protected PasswordService $passwords,
+		protected EventsService $events,
+		protected EmailService $email,
+		protected PasswordGeneratorService $password_generator
 	) {
-		$this->config = $config;
-		$this->translator = $translator;
-		$this->passwords = $passwords;
-		$this->events = $events;
-		$this->email = $email;
-		$this->password_generator = $password_generator;
 	}
 
 	/**
diff --git a/engine/classes/Elgg/Validation/ValidationResult.php b/engine/classes/Elgg/Validation/ValidationResult.php
index 4b8d34e3080..37e888ab439 100644
--- a/engine/classes/Elgg/Validation/ValidationResult.php
+++ b/engine/classes/Elgg/Validation/ValidationResult.php
@@ -7,25 +7,9 @@
  */
 class ValidationResult {
 
-	/**
-	 * @var string
-	 */
-	protected $name;
-
-	/**
-	 * @var mixed
-	 */
-	protected $value;
-
-	/**
-	 * @var string
-	 */
-	protected $message;
+	protected string $message = '';
 
-	/**
-	 * @var string
-	 */
-	protected $error;
+	protected string $error = '';
 
 	/**
 	 * Constructor
@@ -33,9 +17,7 @@ class ValidationResult {
 	 * @param string $name  Parameter name
 	 * @param mixed  $value Parameter value
 	 */
-	public function __construct($name, $value) {
-		$this->name = $name;
-		$this->value = $value;
+	public function __construct(protected string $name, protected $value) {
 	}
 
 	/**
@@ -45,7 +27,7 @@ public function __construct($name, $value) {
 	 *
 	 * @return void
 	 */
-	public function pass($message = '') {
+	public function pass(string $message = ''): void {
 		$this->message = $message;
 	}
 
@@ -56,7 +38,7 @@ public function pass($message = '') {
 	 *
 	 * @return void
 	 */
-	public function fail($error = '') {
+	public function fail(string $error = ''): void {
 		$this->error = $error;
 	}
 
@@ -65,8 +47,8 @@ public function fail($error = '') {
 	 *
 	 * @return bool
 	 */
-	public function isValid() {
-		return !isset($this->error);
+	public function isValid(): bool {
+		return $this->error === '';
 	}
 
 	/**
@@ -74,7 +56,7 @@ public function isValid() {
 	 *
 	 * @return string
 	 */
-	public function getName() {
+	public function getName(): string {
 		return $this->name;
 	}
 
@@ -90,18 +72,18 @@ public function getValue() {
 	/**
 	 * Get error message
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	public function getError() {
+	public function getError(): string {
 		return $this->error;
 	}
 
 	/**
 	 * Get success message
 	 *
-	 * @return mixed
+	 * @return string
 	 */
-	public function getMessage() {
+	public function getMessage(): string {
 		return $this->message;
 	}
 }
diff --git a/engine/classes/Elgg/Views/HtmlFormatter.php b/engine/classes/Elgg/Views/HtmlFormatter.php
index 6488217dd0c..8854adf0999 100644
--- a/engine/classes/Elgg/Views/HtmlFormatter.php
+++ b/engine/classes/Elgg/Views/HtmlFormatter.php
@@ -37,12 +37,6 @@ class HtmlFormatter {
 	 */
 	public const MENTION_REGEX = '/<a[^>]*?>.*?<\/a>|<.*?>|(^|\s|\!|\.|\?|>|\G)+(@([^\s<&]+))/iu';
 
-	protected ViewsService $views;
-
-	protected EventsService $events;
-	
-	protected AutoParagraph $autop;
-
 	/**
 	 * Output constructor.
 	 *
@@ -51,13 +45,10 @@ class HtmlFormatter {
 	 * @param AutoParagraph $autop  Paragraph wrapper
 	 */
 	public function __construct(
-		ViewsService $views,
-		EventsService $events,
-		AutoParagraph $autop
+		protected ViewsService $views,
+		protected EventsService $events,
+		protected AutoParagraph $autop
 	) {
-		$this->views = $views;
-		$this->events = $events;
-		$this->autop = $autop;
 	}
 
 	/**
diff --git a/engine/classes/Elgg/Views/TableColumn/ViewColumn.php b/engine/classes/Elgg/Views/TableColumn/ViewColumn.php
index 65b84c11e0b..9aa8b053abe 100644
--- a/engine/classes/Elgg/Views/TableColumn/ViewColumn.php
+++ b/engine/classes/Elgg/Views/TableColumn/ViewColumn.php
@@ -9,20 +9,7 @@
  */
 class ViewColumn implements TableColumn {
 
-	/**
-	 * @var string
-	 */
-	private $heading;
-
-	/**
-	 * @var string
-	 */
-	private $view;
-
-	/**
-	 * @var array
-	 */
-	private $vars;
+	protected string $heading;
 
 	/**
 	 * Constructor
@@ -31,12 +18,9 @@ class ViewColumn implements TableColumn {
 	 * @param string $heading Heading
 	 * @param array  $vars    Vars to merge into the view vars
 	 */
-	public function __construct($view, $heading = null, $vars = []) {
-		$this->view = $view;
-		$this->vars = $vars;
-
+	public function __construct(protected string $view, string $heading = null, protected array $vars = []) {
 		if (!is_string($heading)) {
-			$heading = elgg_echo("ViewColumn:view:$view");
+			$heading = elgg_echo("ViewColumn:view:{$view}");
 		}
 		
 		$this->heading = $heading;
diff --git a/engine/lib/mb_wrapper.php b/engine/lib/mb_wrapper.php
index b27df24bc4a..923d9304526 100644
--- a/engine/lib/mb_wrapper.php
+++ b/engine/lib/mb_wrapper.php
@@ -77,42 +77,6 @@ function elgg_strpos() {
 	return call_user_func_array('strpos', $args);
 }
 
-/**
- * Wrapper function for mb_strrchr(). Falls back to strrchr() if
- * mb_strrchr() isn't available.  Parameters are passed to the
- * wrapped function in the same order they are passed to this
- * function.
- *
- * @return false|string
- * @since 1.7.0
- */
-function elgg_strrchr() {
-	$args = func_get_args();
-	if (is_callable('mb_strrchr')) {
-		return call_user_func_array('mb_strrchr', $args);
-	}
-	
-	return call_user_func_array('strrchr', $args);
-}
-
-/**
- * Wrapper function for mb_strripos(). Falls back to strripos() if
- * mb_strripos() isn't available.  Parameters are passed to the
- * wrapped function in the same order they are passed to this
- * function.
- *
- * @return false|int
- * @since 1.7.0
- */
-function elgg_strripos() {
-	$args = func_get_args();
-	if (is_callable('mb_strripos')) {
-		return call_user_func_array('mb_strripos', $args);
-	}
-	
-	return call_user_func_array('strripos', $args);
-}
-
 /**
  * Wrapper function for mb_strrpos(). Falls back to strrpos() if
  * mb_strrpos() isn't available.  Parameters are passed to the