diff --git a/fn/auth.php b/fn/auth.php
index 4f321e2..d96d1cb 100644
--- a/fn/auth.php
+++ b/fn/auth.php
@@ -14,47 +14,47 @@ const OPTIONS_PASSWORD = [
 	'threads' => 64,
 ];
 
-function checkUsernameFormat($username) {
+function checkUsernameFormat(string $username): void {
 	if (preg_match('/' . USERNAME_REGEX . '/Du', $username) !== 1)
 		output(403, 'Username malformed.');
 }
 
-function checkPasswordFormat($password) {
+function checkPasswordFormat(string $password): void {
 	if (preg_match('/' . PASSWORD_REGEX . '/Du', $password) !== 1)
 		output(403, 'Password malformed.');
 }
 
-function hashUsername($username) {
+function hashUsername(string $username): string {
 	return base64_encode(sodium_crypto_pwhash(32, $username, hex2bin(query('select', 'params', ['name' => 'username_salt'], 'value')[0]), 2**10, 2**14, SODIUM_CRYPTO_PWHASH_ALG_ARGON2ID13));
 }
 
-function hashPassword($password) {
+function hashPassword(string $password): string {
 	return password_hash($password, ALGO_PASSWORD, OPTIONS_PASSWORD);
 }
 
-function usernameExists($username) {
+function usernameExists(string $username): bool {
 	return isset(query('select', 'users', ['username' => $username], 'id')[0]);
 }
 
-function checkPassword($id, $password) {
+function checkPassword(string $id, string $password): bool {
 	return password_verify($password, query('select', 'users', ['id' => $id], 'password')[0]);
 }
 
-function outdatedPasswordHash($id) {
+function outdatedPasswordHash(string $id): bool {
 	return password_needs_rehash(query('select', 'users', ['id' => $id], 'password')[0], ALGO_PASSWORD, OPTIONS_PASSWORD);
 }
 
-function changePassword($id, $password) {
+function changePassword(string $id, string $password): void {
 	DB->prepare('UPDATE users SET password = :password WHERE id = :id')
 		->execute([':password' => hashPassword($password), ':id' => $id]);
 }
 
-function stopSession() {
+function stopSession(): void {
 	if (session_status() === PHP_SESSION_ACTIVE)
 		session_destroy();
 }
 
-function logout() {
+function logout(): never {
 	stopSession();
 
 	header('Clear-Site-Data: "*"');
@@ -62,7 +62,7 @@ function logout() {
 	redir();
 }
 
-function setupDisplayUsername($display_username) {
+function setupDisplayUsername(string $display_username): void {
 	$nonce = random_bytes(24);
 	$key = sodium_crypto_aead_xchacha20poly1305_ietf_keygen();
 	$cyphertext = sodium_crypto_aead_xchacha20poly1305_ietf_encrypt(
@@ -87,7 +87,7 @@ function setupDisplayUsername($display_username) {
 	$_SESSION['display-username-cyphertext'] = $cyphertext;
 }
 
-function authDeleteUser($user_id) {
+function authDeleteUser(string $user_id): void {
 	$user_services = explode(',', query('select', 'users', ['id' => $user_id], 'services')[0]);
 
 	foreach (SERVICES_USER as $service)
@@ -138,7 +138,7 @@ function authDeleteUser($user_id) {
 	query('delete', 'users', ['id' => $user_id]);
 }
 
-function rateLimit() {
+function rateLimit(): void {
 	if (PAGE_METADATA['tokens_account_cost'] ?? 0 > 0)
 		rateLimitAccount(PAGE_METADATA['tokens_account_cost']);
 
@@ -147,7 +147,7 @@ function rateLimit() {
 }
 
 const MAX_ACCOUNT_TOKENS = 86400;
-function rateLimitAccount($requestedTokens) {
+function rateLimitAccount(int $requestedTokens): int {
 	// Get
 	$userData = query('select', 'users', ['id' => $_SESSION['id']]);
 	$tokens = $userData[0]['bucket_tokens'];
@@ -174,7 +174,7 @@ function rateLimitAccount($requestedTokens) {
 	return $tokens;
 }
 
-function rateLimitInstance($requestedTokens) {
+function rateLimitInstance(int $requestedTokens): void {
 	// Get
 	$tokens = query('select', 'params', ['name' => 'instance_bucket_tokens'], 'value')[0];
 	$bucketLastUpdate = query('select', 'params', ['name' => 'instance_bucket_last_update'], 'value')[0];
diff --git a/fn/common.php b/fn/common.php
index 0002ca1..33815e9 100644
--- a/fn/common.php
+++ b/fn/common.php
@@ -1,6 +1,6 @@
 <?php
 
-function output($code, $msg = '', $logs = [''], $data = []) {
+function output(int $code, string $msg = '', array $logs = [''], array $data = []): never {
 	http_response_code($code);
 	$shortCode = intval($code / 100);
 	if ($shortCode === 5)
@@ -21,7 +21,7 @@ function exescape(array $args, array &$output = NULL, int &$result_code = NULL):
 	return $result_code;
 }
 
-function insert($table, $values) {
+function insert(string $table, array $values): void {
 	$query = 'INSERT INTO "' . $table . '"(';
 
 	foreach ($values as $key => $val) {
@@ -44,7 +44,7 @@ function insert($table, $values) {
 	->execute($values);
 }
 
-function query($action, $table, $conditions = [], $column = NULL) {
+function query(string $action, string $table, array $conditions = [], string $column = NULL): array {
 
 	$query = match ($action) {
 		'select' => 'SELECT *',
@@ -66,7 +66,7 @@ function query($action, $table, $conditions = [], $column = NULL) {
 	return array_column($stmt->fetchAll(PDO::FETCH_ASSOC), $column);
 }
 
-function displayIndex() { ?>
+function displayIndex(): void { ?>
 <nav>
 	<dl>
 <?php foreach (PAGES[SERVICE] as $pageId => $page) {
@@ -82,11 +82,11 @@ function displayIndex() { ?>
 <?php
 }
 
-function redirUrl($pageId) {
+function redirUrl(string $pageId): string {
 	return CONF['common']['prefix'] . '/' . $pageId . '?redir=' . PAGE_URL;
 }
 
-function redir($redir_to = NULL) {
+function redir(string $redir_to = NULL): never {
 	$redir_to ??= $_GET['redir'] ?? NULL;
 
 	if ($redir_to === NULL) {
@@ -100,7 +100,7 @@ function redir($redir_to = NULL) {
 }
 
 // PHP rmdir() only works on empty directories
-function removeDirectory($dir) {
+function removeDirectory(string $dir): void {
 	$dirObj = new RecursiveDirectoryIterator($dir, RecursiveDirectoryIterator::SKIP_DOTS);
 	$files = new RecursiveIteratorIterator($dirObj, RecursiveIteratorIterator::CHILD_FIRST);
 	foreach ($files as $file)
@@ -109,7 +109,7 @@ function removeDirectory($dir) {
 		output(500, 'Unable to remove directory.');
 }
 
-function equalArrays($a, $b) {
+function equalArrays(array $a, array $b): bool {
 	return array_diff($a, $b) === [] AND array_diff($b, $a) === [];
 }
 
@@ -126,12 +126,12 @@ if (time() - query('select', 'params', ['name' => 'secret_key_last_change'], 'va
 	->execute([':last_change' => time()]);
 }
 define('SECRET_KEY', hex2bin(query('select', 'params', ['name' => 'secret_key'], 'value')[0]));
-function getAuthToken() {
+function getAuthToken(): string {
 	$salt = bin2hex(random_bytes(4));
 	$hash = hash_hmac('sha256', $salt . ($_SESSION['id'] ?? ''), SECRET_KEY);
 	return $salt . '-' .  substr($hash, 0, 32);
 }
-function checkAuthToken($salt, $hash) {
+function checkAuthToken(string $salt, string $hash): void {
 	$correctProof = substr(hash_hmac('sha256', $salt . $_SESSION['id'], SECRET_KEY), 0, 32);
 	if (hash_equals($correctProof, $hash) !== true)
 		output(403, _('Wrong proof.'));
diff --git a/fn/dns.php b/fn/dns.php
index ef4f803..6c4b171 100644
--- a/fn/dns.php
+++ b/fn/dns.php
@@ -1,6 +1,6 @@
 <?php
 
-function parseZoneFile($zone_content, $types, $filter_domain = false) {
+function parseZoneFile(string $zone_content, array $types, bool|string $filter_domain = false): array {
 	$parsed_zone_content = [];
 	foreach (explode(LF, $zone_content) as $zone_line) {
 		if ($zone_line === '' OR str_starts_with($zone_line, ';'))
@@ -46,7 +46,7 @@ function knotcConfExec(array $cmds): void {
 	}
 }
 
-function knotcZoneExec(string $zone, array $cmd, string $action = NULL) {
+function knotcZoneExec(string $zone, array $cmd, string $action = NULL): void {
 	$action = checkAction($action ?? $_POST['action']);
 
 	knotc(['zone-begin', $zone], $output['begin'], $code['begin']);
@@ -66,7 +66,7 @@ function knotcZoneExec(string $zone, array $cmd, string $action = NULL) {
 	}
 }
 
-function checkIpFormat($ip) {
+function checkIpFormat(string $ip): string {
 	if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4))
 		return 'A';
 	if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6))
@@ -74,24 +74,24 @@ function checkIpFormat($ip) {
 	output(403, _('IP address malformed.'));
 }
 
-function checkAbsoluteDomainFormat($domain) { // If the domain must end with a dot
+function checkAbsoluteDomainFormat(string $domain): void { // If the domain must end with a dot
 	if (!filter_var($domain, FILTER_VALIDATE_DOMAIN) OR preg_match('/^(?=^.{1,254}$)([a-z0-9_-]{1,63}\.){2,127}$/D', $domain) !== 1)
 		output(403, _('Domain malformed.'));
 }
 
-function formatEndWithDot($str) {
+function formatEndWithDot(string $str): string {
 	if (!str_ends_with($str, '.'))
 		$str .= '.';
 	return $str;
 }
 
-function formatAbsoluteDomain($domain) {
+function formatAbsoluteDomain(string $domain): string {
 	$domain = formatEndWithDot(strtolower($domain));
 	checkAbsoluteDomainFormat($domain);
 	return $domain;
 }
 
-function checkAction($action) {
+function checkAction(string $action): string {
 	return match ($action) {
 		'add' => '',
 		'delete' => 'un',
diff --git a/fn/ht.php b/fn/ht.php
index 8b9e3d5..75d03a3 100644
--- a/fn/ht.php
+++ b/fn/ht.php
@@ -3,7 +3,7 @@
 const SUBPATH_REGEX = '^[a-z0-9-]{4,63}$';
 const ED25519_PUBKEY_REGEX = '^[a-zA-Z0-9/+]{68}$';
 
-function htSetupUserFs($id) {
+function htSetupUserFs(string $id): void {
 	// Setup SFTP directory
 	if (mkdir(CONF['ht']['ht_path'] . '/fs/' . $id, 0000) !== true)
 		output(500, 'Can\'t create user directory.');
@@ -42,19 +42,19 @@ function htSetupUserFs($id) {
 		output(500, 'Can\'t create Tor keys directory.');
 }
 
-function checkDomainFormat($domain) {
+function checkDomainFormat(string $domain): void {
 	// If the domain must end without a dot
 	if (!filter_var($domain, FILTER_VALIDATE_DOMAIN) OR !preg_match('/^(?=^.{1,254}$)([a-z0-9_-]{1,63}\.){1,126}[a-z0-9]{1,63}$/D', $domain))
 		output(403, _('Domain malformed.'));
 }
 
-function formatDomain($domain) {
+function formatDomain(string $domain): string {
 	$domain = rtrim(strtolower($domain), '.');
 	checkDomainFormat($domain);
 	return $domain;
 }
 
-function listFsDirs($username) {
+function listFsDirs(string $username): array {
 	if ($username === '')
 		return [];
 	$absoluteDirs = glob(CONF['ht']['ht_path'] . '/fs/' . $username . '/*/', GLOB_ONLYDIR);
@@ -65,7 +65,7 @@ function listFsDirs($username) {
 	return $dirs;
 }
 
-function addSite($username, $siteDir, $address, $type) {
+function addSite(string $username, string $siteDir, string $address, string $type): void {
 	insert('sites', [
 		'username' => $username,
 		'site_dir' => $siteDir,
@@ -75,7 +75,7 @@ function addSite($username, $siteDir, $address, $type) {
 	]);
 }
 
-function dirsStatuses($type) {
+function dirsStatuses(string $type): array {
 	if (isset($_SESSION['id']) !== true)
 		return [];
 	$dbDirs = query('select', 'sites', [
@@ -88,7 +88,7 @@ function dirsStatuses($type) {
 	return $dirs;
 }
 
-function htRelativeSymlink($target, $name) {
+function htRelativeSymlink(string $target, string $name): void {
 	chdir(pathinfo($name)['dirname']);
 	$symlink = symlink($target, pathinfo($name)['basename']);
 	chdir(ROOT_PATH);
@@ -96,7 +96,7 @@ function htRelativeSymlink($target, $name) {
 		output(500, 'Unable to create symlink.');
 }
 
-function htDeleteSite($address, $type, $user_id) {
+function htDeleteSite(string $address, string $type, string $user_id): void {
 
 	if ($type === 'onion') {
 		$dir = query('select', 'sites', [
diff --git a/fn/ns.php b/fn/ns.php
index a93e82c..a659385 100644
--- a/fn/ns.php
+++ b/fn/ns.php
@@ -17,7 +17,7 @@ const ALLOWED_TYPES = ['AAAA', 'A', 'TXT', 'SRV', 'MX', 'SVCB', 'HTTPS', 'NS', '
 
 const ZONE_MAX_CHARACTERS = 10000;
 
-function nsParseCommonRequirements() {
+function nsParseCommonRequirements(): array {
 	nsCheckZonePossession($_POST['zone']);
 
 	if (($_POST['subdomain'] === '') OR ($_POST['subdomain'] === '@'))
@@ -35,20 +35,20 @@ function nsParseCommonRequirements() {
 	return $values;
 }
 
-function nsListUserZones() {
+function nsListUserZones(): array {
 	if (isset($_SESSION['id']))
 		return query('select', 'zones', ['username' => $_SESSION['id']], 'zone');
 	return [];
 }
 
-function nsCheckZonePossession($zone) {
+function nsCheckZonePossession(string $zone): void {
 	checkAbsoluteDomainFormat($zone);
 
 	if (!in_array($zone, nsListUserZones(), true))
 		output(403, 'You don\'t own this zone on the name server.');
 }
 
-function nsDeleteZone($zone, $user_id) {
+function nsDeleteZone(string $zone, string $user_id): void {
 	// Remove from Knot configuration
 	knotcConfExec([['conf-unset', 'zone[' . $zone . ']']]);
 
diff --git a/fn/reg.php b/fn/reg.php
index 0a5f981..c49e6c4 100644
--- a/fn/reg.php
+++ b/fn/reg.php
@@ -2,18 +2,18 @@
 
 const SUBDOMAIN_REGEX = '^(?!\-)(?!..\-\-)[a-z0-9-]{4,63}(?<!\-)$';
 
-function regListUserDomains() {
+function regListUserDomains(): array {
 	if (isset($_SESSION['id']))
 		return query('select', 'registry', ['username' => $_SESSION['id']], 'domain');
 	return [];
 }
 
-function regCheckDomainPossession($domain) {
+function regCheckDomainPossession(string $domain): void {
 	if (in_array($domain, regListUserDomains(), true) !== true)
 		output(403, 'You don\'t own this domain on the registry.');
 }
 
-function regDeleteDomain($domain, $user_id) {
+function regDeleteDomain(string $domain, string $user_id): void {
 	// Delete domain from registry file
 	$path = CONF['reg']['suffixes_path'] . '/' . regParseDomain($domain)['suffix'] . 'zone';
 	$content = file_get_contents($path);
@@ -46,7 +46,7 @@ function regDeleteDomain($domain, $user_id) {
 	}
 }
 
-function regParseDomain($domain) {
+function regParseDomain(string $domain): array {
 	$parts = explode('.', $domain, 2);
 	$subdomain = $parts[0];
 	$suffix = $parts[1];
diff --git a/init.php b/init.php
index 703cd93..c85e75c 100644
--- a/init.php
+++ b/init.php
@@ -5,7 +5,7 @@ set_error_handler(function ($level, $message, $file = '', $line = 0) {
 	throw new ErrorException($message, 0, $level, $file, $line);
 });
 set_exception_handler(function ($e) {
-	error_log($e);
+	error_log($e->getMessage());
 	http_response_code(500);
 	echo '<h1>Error</h1>An error occured.';
 });
diff --git a/jobs/check.php b/jobs/check.php
index 733447b..a6dc279 100644
--- a/jobs/check.php
+++ b/jobs/check.php
@@ -18,7 +18,7 @@ if (preg_match('/^;; Flags: qr rd ra ad;/Dm', implode("\n", $output)) !== 1)
 
 define('COOKIE_FILE', sys_get_temp_dir() . '/cookie-' . bin2hex(random_bytes(16)) . '.txt');
 
-function curlTest($address, $post = [], $tor = false) {
+function curlTest(string $address, array $post = [], bool $tor = false): string {
 	$req = curl_init();
 	curl_setopt($req, CURLOPT_RETURNTRANSFER, true);
 
@@ -85,7 +85,7 @@ curlTest('/auth/username', [
 
 echo 'Created account with username "' . $username . '" and password "' . $password . '".' . LF;
 
-function testReg() {
+function testReg(): string {
 	$subdomain = bin2hex(random_bytes(16));
 
 	curlTest('/reg/register', [
@@ -119,7 +119,7 @@ function testReg() {
 	return $domain;
 }
 
-function testNs($domain) {
+function testNs(string $domain): void {
 	foreach (CONF['ns']['servers'] as $ns)
 		curlTest('/reg/ns', [
 			'action' => 'add',
@@ -178,7 +178,7 @@ function testNs($domain) {
 		exit('Error: /ns/edit: AAAA record not set' . LF);
 }
 
-function testHt($username, $password) {
+function testHt(string $username, string $password): void {
 	define('TEST_CONTENT', 'test-' . bin2hex(random_bytes(16)));
 
 	file_put_contents(sys_get_temp_dir() . '/index.html', TEST_CONTENT);
diff --git a/pg-act/reg/register.php b/pg-act/reg/register.php
index f516c45..ad590f7 100644
--- a/pg-act/reg/register.php
+++ b/pg-act/reg/register.php
@@ -53,7 +53,7 @@ if ($blocked OR $registration_data !== [])
 if ($_POST['action'] !== 'register')
 	message($message . ' ✔️ ' . _('This domain is open to registration!'));
 
-function message($message) {
+function message(string $message): never {
 	output(200, data: [
 		'message' => '<p>' . $message . '</p>',
 		'domain' => htmlspecialchars($_POST['subdomain']),
diff --git a/router.php b/router.php
index a977203..0c0a024 100644
--- a/router.php
+++ b/router.php
@@ -11,7 +11,7 @@ define('PAGE_ADDRESS', $pageAddress . ((substr($pageAddress, -1) === '/' OR $pag
 define('PAGE_LINEAGE', explode('/', PAGE_ADDRESS));
 define('SERVICE', dirname(PAGE_ADDRESS));
 
-function getPageInformations($pages, $pageElements) {
+function getPageInformations(array $pages, array $pageElements): array {
 	if (!isset($pages['index']) OR $pageElements[0] === 'index')
 		return [
 			'titles_lineage' => [$pages[$pageElements[0]]['title'] ?? false],
@@ -44,7 +44,7 @@ if (in_array($_SERVER['SERVER_NAME'], CONF['common']['public_domains'], true) !=
 define('SERVER_NAME', $_SERVER['SERVER_NAME']);
 
 const SESSION_COOKIE_NAME = 'servnest-session-key';
-function startSession() {
+function startSession(): void {
 	session_start([
 		'name' => SESSION_COOKIE_NAME,
 		'sid_length' => 64,
@@ -94,7 +94,7 @@ if (isset($_SESSION['id'])) {
 		}
 }
 
-function displayFinalMessage($data) {
+function displayFinalMessage(?array $data): void {
 	if (isset($data['final_message'])) {
 		echo $data['final_message'];
 		unset($data['final_message']);
@@ -118,7 +118,7 @@ if ($_POST !== []) {
 		require ROOT_PATH . '/pg-act/' . PAGE_ADDRESS . '.php';
 }
 
-function displayPage($data) {
+function displayPage(?array $data): never {
 	require ROOT_PATH . '/view.php';
 	exit();
 }
diff --git a/sftpgo-auth.php b/sftpgo-auth.php
index fa474a0..6ec3ef8 100644
--- a/sftpgo-auth.php
+++ b/sftpgo-auth.php
@@ -5,7 +5,7 @@ const DEBUG = false;
 
 require 'init.php';
 
-function deny($reason) {
+function deny(string $reason): never {
 	!DEBUG or file_put_contents(ROOT_PATH . '/db/debug.txt', ob_get_contents() . $reason . LF);
 	http_response_code(403);
 	exit();