diff --git a/README.md b/README.md
index d1efc1e..97cb699 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,5 @@
 # Icinga PHP Library - SQL abstraction layer
 
-![Build Status](https://github.com/Icinga/ipl-sql/workflows/PHP%20Tests/badge.svg?branch=main)
-
 The package `ipl\Sql` provides a [database connection
 abstraction](#sql-connection) and an [SQL query abstraction layer](#sql-queries)
 for building SQL queries via an OOP API.
diff --git a/phpstan.neon b/phpstan.neon
index f58b54c..5ee24f4 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -11,9 +11,6 @@ parameters:
     paths:
         - src
 
-    scanDirectories:
-        - vendor
-
     universalObjectCratesClasses: # to ignore magic property errors
         - ipl\Sql\Config
 
diff --git a/src/Adapter/BaseAdapter.php b/src/Adapter/BaseAdapter.php
index f062f63..29994f3 100644
--- a/src/Adapter/BaseAdapter.php
+++ b/src/Adapter/BaseAdapter.php
@@ -21,13 +21,13 @@ abstract class BaseAdapter implements Adapter
      *
      * @var array
      */
-    protected $quoteCharacter = ['"', '"'];
+    protected array $quoteCharacter = ['"', '"'];
 
     /** @var string Character to use for escaping quote characters */
-    protected $escapeCharacter = '\\"';
+    protected string $escapeCharacter = '\\"';
 
     /** @var array Default PDO connect options */
-    protected $options = [
+    protected array $options = [
         PDO::ATTR_CASE => PDO::CASE_NATURAL,
         PDO::ATTR_EMULATE_PREPARES => false,
         PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
@@ -35,7 +35,7 @@ abstract class BaseAdapter implements Adapter
         PDO::ATTR_STRINGIFY_FETCHES => false
     ];
 
-    public function getDsn(Config $config)
+    public function getDsn(Config $config): string
     {
         $dsn = "{$config->db}:";
 
@@ -50,7 +50,7 @@ public function getDsn(Config $config)
         return $dsn . implode(';', $parts);
     }
 
-    public function getOptions(Config $config)
+    public function getOptions(Config $config): array
     {
         if (is_array($config->options)) {
             return $config->options + $this->options;
@@ -59,12 +59,12 @@ public function getOptions(Config $config)
         return $this->options;
     }
 
-    public function setClientTimezone(Connection $db)
+    public function setClientTimezone(Connection $db): static
     {
         return $this;
     }
 
-    public function quoteIdentifier($identifiers)
+    public function quoteIdentifier(array|string $identifiers): string
     {
         if (is_string($identifiers)) {
             $identifiers = explode('.', $identifiers);
@@ -83,7 +83,7 @@ public function quoteIdentifier($identifiers)
         return implode('.', $identifiers);
     }
 
-    public function registerQueryBuilderCallbacks(QueryBuilder $queryBuilder)
+    public function registerQueryBuilderCallbacks(QueryBuilder $queryBuilder): static
     {
         $queryBuilder->on(QueryBuilder::ON_ASSEMBLE_SELECT, function (Select $select): void {
             if ($select->hasOrderBy()) {
@@ -105,7 +105,7 @@ public function registerQueryBuilderCallbacks(QueryBuilder $queryBuilder)
         return $this;
     }
 
-    protected function getTimezoneOffset()
+    protected function getTimezoneOffset(): string
     {
         $tz = new DateTimeZone(date_default_timezone_get());
         $offset = $tz->getOffset(new DateTime());
diff --git a/src/Adapter/Mssql.php b/src/Adapter/Mssql.php
index c9f11ce..55d6c95 100644
--- a/src/Adapter/Mssql.php
+++ b/src/Adapter/Mssql.php
@@ -10,11 +10,11 @@
 
 class Mssql extends BaseAdapter
 {
-    protected $quoteCharacter = ['[', ']'];
+    protected array $quoteCharacter = ['[', ']'];
 
-    protected $escapeCharacter = '[[]';
+    protected string $escapeCharacter = '[[]';
 
-    public function getDsn(Config $config)
+    public function getDsn(Config $config): string
     {
         $drivers = array_intersect(['sqlsrv', 'dblib', 'mssql', 'sybase'], PDO::getAvailableDrivers());
 
@@ -62,7 +62,7 @@ public function getDsn(Config $config)
         return $dsn;
     }
 
-    public function registerQueryBuilderCallbacks(QueryBuilder $queryBuilder)
+    public function registerQueryBuilderCallbacks(QueryBuilder $queryBuilder): static
     {
         parent::registerQueryBuilderCallbacks($queryBuilder);
 
diff --git a/src/Adapter/Mysql.php b/src/Adapter/Mysql.php
index 2421cae..19683b3 100644
--- a/src/Adapter/Mysql.php
+++ b/src/Adapter/Mysql.php
@@ -4,51 +4,57 @@
 
 use ipl\Sql\Config;
 use ipl\Sql\Connection;
-use PDO;
 
 class Mysql extends BaseAdapter
 {
-    protected $quoteCharacter = ['`', '`'];
+    protected array $quoteCharacter = ['`', '`'];
 
-    protected $escapeCharacter = '``';
+    protected string $escapeCharacter = '``';
 
-    public function setClientTimezone(Connection $db)
+    public function setClientTimezone(Connection $db): static
     {
         $db->exec('SET time_zone = ' . $db->quote($this->getTimezoneOffset()));
 
         return $this;
     }
 
-    public function getOptions(Config $config)
+    public function getOptions(Config $config): array
     {
         $options = parent::getOptions($config);
+        // In PHP 8.5+, driver-specific constants of the PDO class are deprecated,
+        // but the replacements are only available since php 8.4
+        if (version_compare(PHP_VERSION, '8.4.0', '<')) {
+            $mysqlConstantPrefix = 'PDO::MYSQL_ATTR_';
+        } else {
+            $mysqlConstantPrefix = 'Pdo\Mysql::ATTR_';
+        }
 
         if (! empty($config->useSsl)) {
             if (! empty($config->sslKey)) {
-                $options[PDO::MYSQL_ATTR_SSL_KEY] = $config->sslKey;
+                $options[constant($mysqlConstantPrefix . 'SSL_KEY')] = $config->sslKey;
             }
 
             if (! empty($config->sslCert)) {
-                $options[PDO::MYSQL_ATTR_SSL_CERT] = $config->sslCert;
+                $options[constant($mysqlConstantPrefix . 'SSL_CERT')] = $config->sslCert;
             }
 
             if (! empty($config->sslCa)) {
-                $options[PDO::MYSQL_ATTR_SSL_CA] = $config->sslCa;
+                $options[constant($mysqlConstantPrefix . 'SSL_CA')] = $config->sslCa;
             }
 
             if (! empty($config->sslCapath)) {
-                $options[PDO::MYSQL_ATTR_SSL_CAPATH] = $config->sslCapath;
+                $options[constant($mysqlConstantPrefix . 'SSL_CAPATH')] = $config->sslCapath;
             }
 
             if (! empty($config->sslCipher)) {
-                $options[PDO::MYSQL_ATTR_SSL_CIPHER] = $config->sslCipher;
+                $options[constant($mysqlConstantPrefix . 'SSL_CIPHER')] = $config->sslCipher;
             }
 
             if (
-                defined('PDO::MYSQL_ATTR_SSL_VERIFY_SERVER_CERT')
+                defined($mysqlConstantPrefix . 'SSL_VERIFY_SERVER_CERT')
                 && ! empty($config->sslDoNotVerifyServerCert)
             ) {
-                $options[PDO::MYSQL_ATTR_SSL_VERIFY_SERVER_CERT] = false;
+                $options[constant($mysqlConstantPrefix . 'SSL_VERIFY_SERVER_CERT')] = false;
             }
         }
 
diff --git a/src/Adapter/Oracle.php b/src/Adapter/Oracle.php
index de0aee5..a6c5aa0 100644
--- a/src/Adapter/Oracle.php
+++ b/src/Adapter/Oracle.php
@@ -7,7 +7,7 @@
 
 class Oracle extends BaseAdapter
 {
-    public function getDsn(Config $config)
+    public function getDsn(Config $config): string
     {
         $dsn = 'oci:dbname=';
 
@@ -30,7 +30,7 @@ public function getDsn(Config $config)
         return $dsn;
     }
 
-    public function setClientTimezone(Connection $db)
+    public function setClientTimezone(Connection $db): static
     {
         $db->prepexec('ALTER SESSION SET TIME_ZONE = ?', [$this->getTimezoneOffset()]);
 
diff --git a/src/Adapter/Pgsql.php b/src/Adapter/Pgsql.php
index 18bf15d..871d059 100644
--- a/src/Adapter/Pgsql.php
+++ b/src/Adapter/Pgsql.php
@@ -6,7 +6,7 @@
 
 class Pgsql extends BaseAdapter
 {
-    public function setClientTimezone(Connection $db)
+    public function setClientTimezone(Connection $db): static
     {
         $db->exec(sprintf('SET TIME ZONE INTERVAL %s HOUR TO MINUTE', $db->quote($this->getTimezoneOffset())));
 
diff --git a/src/Adapter/Sqlite.php b/src/Adapter/Sqlite.php
index 9f4e209..e040b6f 100644
--- a/src/Adapter/Sqlite.php
+++ b/src/Adapter/Sqlite.php
@@ -6,7 +6,7 @@
 
 class Sqlite extends BaseAdapter
 {
-    public function getDsn(Config $config)
+    public function getDsn(Config $config): string
     {
         return "sqlite:{$config->dbname}";
     }
diff --git a/src/CommonTableExpression.php b/src/CommonTableExpression.php
index 596ec39..5877fbf 100644
--- a/src/CommonTableExpression.php
+++ b/src/CommonTableExpression.php
@@ -17,21 +17,21 @@ trait CommonTableExpression
      *
      * @var array[]
      */
-    protected $with = [];
+    protected array $with = [];
 
-    public function getWith()
+    public function getWith(): array
     {
         return $this->with;
     }
 
-    public function with(Select $query, $alias, $recursive = false)
+    public function with(Select $query, string $alias, bool $recursive = false): static
     {
         $this->with[] = [$query, $alias, $recursive];
 
         return $this;
     }
 
-    public function resetWith()
+    public function resetWith(): static
     {
         $this->with = [];
 
@@ -43,7 +43,7 @@ public function resetWith()
      *
      * Shall be called by using classes in their __clone()
      */
-    protected function cloneCte()
+    protected function cloneCte(): void
     {
         foreach ($this->with as &$cte) {
             $cte[0] = clone $cte[0];
diff --git a/src/CommonTableExpressionInterface.php b/src/CommonTableExpressionInterface.php
index 7e93bc8..9a528bd 100644
--- a/src/CommonTableExpressionInterface.php
+++ b/src/CommonTableExpressionInterface.php
@@ -17,7 +17,7 @@ interface CommonTableExpressionInterface
      *
      * @return array[]
      */
-    public function getWith();
+    public function getWith(): array;
 
     /**
      * Add a CTE
@@ -28,12 +28,12 @@ public function getWith();
      *
      * @return $this
      */
-    public function with(Select $query, $alias, $recursive = false);
+    public function with(Select $query, string $alias, bool $recursive = false): static;
 
     /**
      * Reset all CTEs
      *
      * @return $this
      */
-    public function resetWith();
+    public function resetWith(): static;
 }
diff --git a/src/Compat/FilterProcessor.php b/src/Compat/FilterProcessor.php
index 1ed1c3d..457b712 100644
--- a/src/Compat/FilterProcessor.php
+++ b/src/Compat/FilterProcessor.php
@@ -13,7 +13,7 @@
 
 class FilterProcessor
 {
-    public static function assembleFilter(Filter\Rule $filter, $level = 0)
+    public static function assembleFilter(Filter\Rule $filter, int $level = 0): ?array
     {
         $condition = null;
 
@@ -60,7 +60,7 @@ public static function assembleFilter(Filter\Rule $filter, $level = 0)
         return $condition;
     }
 
-    public static function assemblePredicate(Filter\Condition $filter)
+    public static function assemblePredicate(Filter\Condition $filter): array
     {
         $column = $filter->getColumn();
         $expression = $filter->getValue();
diff --git a/src/Config.php b/src/Config.php
index 5fa103e..e4fdb49 100644
--- a/src/Config.php
+++ b/src/Config.php
@@ -2,34 +2,31 @@
 
 namespace ipl\Sql;
 
-use InvalidArgumentException;
 use ipl\Stdlib\Str;
 use OutOfRangeException;
 
-use function ipl\Stdlib\get_php_type;
-
 /**
  * SQL connection configuration
  */
 class Config
 {
-    /** @var string Type of the DBMS */
-    public $db;
+    /** @var ?string Type of the DBMS */
+    public ?string $db = null;
 
-    /** @var string Database host */
-    public $host;
+    /** @var ?string Database host */
+    public ?string $host = null;
 
-    /** @var int Database port */
-    public $port;
+    /** @var string|int|null Database port */
+    public string|int|null $port = null;
 
-    /** @var string Database name */
-    public $dbname;
+    /** @var ?string Database name */
+    public ?string $dbname = null;
 
-    /** @var string Username to use for authentication */
-    public $username;
+    /** @var ?string Username to use for authentication */
+    public ?string $username = null;
 
-    /** @var string Password to use for authentication */
-    public $password;
+    /** @var ?string Password to use for authentication */
+    public ?string $password = null;
 
     /**
      * Character set for the connection
@@ -38,7 +35,7 @@ class Config
      *
      * @var string
      */
-    public $charset;
+    public string $charset = '';
 
     /**
      * PDO connect options
@@ -48,10 +45,10 @@ class Config
      *
      * @var array
      */
-    public $options;
+    public array $options = [];
 
     /** @var array Extra settings e.g. for SQL SSL connections */
-    protected $extraSettings = [];
+    protected array $extraSettings = [];
 
     /**
      * Create a new SQL connection configuration from the given configuration key-value pairs
@@ -59,19 +56,9 @@ class Config
      * Keys will be converted to camelCase, e.g. use_ssl → useSsl.
      *
      * @param iterable $config Configuration key-value pairs
-     *
-     * @throws InvalidArgumentException If $config is not iterable
      */
-    public function __construct($config)
+    public function __construct(iterable $config)
     {
-        if (! is_iterable($config)) {
-            throw new InvalidArgumentException(sprintf(
-                '%s expects parameter one to be iterable, got %s instead',
-                __METHOD__,
-                get_php_type($config)
-            ));
-        }
-
         foreach ($config as $key => $value) {
             $key = Str::camel($key);
             $this->$key = $value;
diff --git a/src/Connection.php b/src/Connection.php
index 9480fe7..40b41d3 100644
--- a/src/Connection.php
+++ b/src/Connection.php
@@ -4,6 +4,7 @@
 
 use BadMethodCallException;
 use Exception;
+use Generator;
 use InvalidArgumentException;
 use ipl\Sql\Contract\Adapter;
 use ipl\Sql\Contract\Quoter;
@@ -11,6 +12,7 @@
 use LogicException;
 use PDO;
 use PDOStatement;
+use Throwable;
 
 /**
  * Connection to a SQL database using the native PDO for database access
@@ -20,27 +22,27 @@ class Connection implements Quoter
     use Plugins;
 
     /** @var Config */
-    protected $config;
+    protected Config $config;
 
     /** @var ?PDO */
-    protected $pdo;
+    protected ?PDO $pdo = null;
 
-    /** @var QueryBuilder */
-    protected $queryBuilder;
+    /** @var ?QueryBuilder */
+    protected ?QueryBuilder $queryBuilder = null;
 
     /** @var Adapter */
-    protected $adapter;
+    protected Adapter $adapter;
 
     /**
      * Create a new database connection using the given config for initialising the options for the connection
      *
      * {@link init()} is called after construction.
      *
-     * @param Config|iterable $config
+     * @param iterable|Config $config
      *
      * @throws InvalidArgumentException If there's no adapter for the given database available
      */
-    public function __construct($config)
+    public function __construct(iterable|Config $config)
     {
         $config = $config instanceof Config ? $config : new Config($config);
 
@@ -69,7 +71,7 @@ public function __construct($config)
      * @throws BadMethodCallException If the called method does not exist
      *
      */
-    public function __call($name, array $arguments)
+    public function __call(string $name, array $arguments)
     {
         $this->connect();
 
@@ -88,7 +90,7 @@ public function __call($name, array $arguments)
      *
      * If you have to adjust the connection after construction, override this method.
      */
-    public function init()
+    public function init(): void
     {
     }
 
@@ -97,7 +99,7 @@ public function init()
      *
      * @return Adapter
      */
-    public function getAdapter()
+    public function getAdapter(): Adapter
     {
         return $this->adapter;
     }
@@ -107,7 +109,7 @@ public function getAdapter()
      *
      * @return Config
      */
-    public function getConfig()
+    public function getConfig(): Config
     {
         return $this->config;
     }
@@ -117,7 +119,7 @@ public function getConfig()
      *
      * @return QueryBuilder
      */
-    public function getQueryBuilder()
+    public function getQueryBuilder(): QueryBuilder
     {
         if ($this->queryBuilder === null) {
             $this->queryBuilder = new QueryBuilder($this->adapter);
@@ -134,7 +136,7 @@ public function getQueryBuilder()
      *
      * @return PDO
      */
-    protected function createPdoAdapter()
+    protected function createPdoAdapter(): PDO
     {
         $adapter = $this->getAdapter();
 
@@ -153,7 +155,7 @@ protected function createPdoAdapter()
      *
      * @return $this
      */
-    public function connect()
+    public function connect(): static
     {
         if ($this->pdo !== null) {
             return $this;
@@ -175,7 +177,7 @@ public function connect()
      *
      * @return $this
      */
-    public function disconnect()
+    public function disconnect(): static
     {
         $this->pdo = null;
 
@@ -189,11 +191,11 @@ public function disconnect()
      *
      * @return bool
      */
-    public function ping($reconnect = true)
+    public function ping(bool $reconnect = true): bool
     {
         try {
             $this->query('SELECT 1')->closeCursor();
-        } catch (Exception $e) {
+        } catch (Throwable) {
             if (! $reconnect) {
                 return false;
             }
@@ -210,11 +212,11 @@ public function ping($reconnect = true)
      * Fetch and return all result rows as sequential array
      *
      * @param Select|string $stmt   The SQL statement to prepare and execute.
-     * @param array         $values Values to bind to the statement
+     * @param ?array        $values Values to bind to the statement
      *
      * @return array
      */
-    public function fetchAll($stmt, array $values = null)
+    public function fetchAll(Select|string $stmt, ?array $values = null): array
     {
         return $this->prepexec($stmt, $values)
             ->fetchAll();
@@ -224,11 +226,11 @@ public function fetchAll($stmt, array $values = null)
      * Fetch and return the first column of all result rows as sequential array
      *
      * @param Select|string $stmt   The SQL statement to prepare and execute.
-     * @param array         $values Values to bind to the statement
+     * @param ?array        $values Values to bind to the statement
      *
      * @return array
      */
-    public function fetchCol($stmt, array $values = null)
+    public function fetchCol(Select|string $stmt, ?array $values = null): array
     {
         return $this->prepexec($stmt, $values)
             ->fetchAll(PDO::FETCH_COLUMN, 0);
@@ -238,11 +240,11 @@ public function fetchCol($stmt, array $values = null)
      * Fetch and return the first row of the result rows
      *
      * @param Select|string $stmt   The SQL statement to prepare and execute.
-     * @param array         $values Values to bind to the statement
+     * @param ?array        $values Values to bind to the statement
      *
-     * @return array
+     * @return mixed
      */
-    public function fetchOne($stmt, array $values = null)
+    public function fetchOne(Select|string $stmt, ?array $values = null): mixed
     {
         return $this->prepexec($stmt, $values)
             ->fetch();
@@ -251,7 +253,7 @@ public function fetchOne($stmt, array $values = null)
     /**
      * Alias of {@link fetchOne()}
      */
-    public function fetchRow($stmt, array $values = null)
+    public function fetchRow(Select|string $stmt, ?array $values = null): mixed
     {
         return $this->prepexec($stmt, $values)
             ->fetch();
@@ -263,11 +265,11 @@ public function fetchRow($stmt, array $values = null)
      * First column is the key and the second column is the value.
      *
      * @param Select|string $stmt   The SQL statement to prepare and execute.
-     * @param array         $values Values to bind to the statement
+     * @param ?array        $values Values to bind to the statement
      *
      * @return array
      */
-    public function fetchPairs($stmt, array $values = null)
+    public function fetchPairs(Select|string $stmt, ?array $values = null): array
     {
         return $this->prepexec($stmt, $values)
             ->fetchAll(PDO::FETCH_KEY_PAIR);
@@ -277,11 +279,11 @@ public function fetchPairs($stmt, array $values = null)
      * Fetch and return the first column of the first result row
      *
      * @param Select|string $stmt   The SQL statement to prepare and execute.
-     * @param array         $values Values to bind to the statement
+     * @param ?array        $values Values to bind to the statement
      *
-     * @return string
+     * @return mixed
      */
-    public function fetchScalar($stmt, array $values = null)
+    public function fetchScalar(Select|string $stmt, ?array $values = null): mixed
     {
         return $this->prepexec($stmt, $values)
             ->fetchColumn(0);
@@ -295,9 +297,9 @@ public function fetchScalar($stmt, array $values = null)
      * @param Select|string $stmt    The SQL statement to prepare and execute.
      * @param mixed         ...$args Values to bind to the statement, fetch mode for the statement, fetch mode options
      *
-     * @return \Generator
+     * @return Generator
      */
-    public function yieldAll($stmt, ...$args)
+    public function yieldAll(Select|string $stmt, ...$args): Generator
     {
         $values = null;
 
@@ -343,11 +345,11 @@ public function yieldAll($stmt, ...$args)
      * Yield the first column of each result row
      *
      * @param Select|string $stmt   The SQL statement to prepare and execute
-     * @param array         $values Values to bind to the statement
+     * @param ?array        $values Values to bind to the statement
      *
-     * @return \Generator
+     * @return Generator
      */
-    public function yieldCol($stmt, array $values = null)
+    public function yieldCol(Select|string $stmt, ?array $values = null): Generator
     {
         $sth = $this->prepexec($stmt, $values);
 
@@ -362,18 +364,18 @@ public function yieldCol($stmt, array $values = null)
      * Yield key-value pairs with the first column as key and the second column as value for each result row
      *
      * @param Select|string $stmt   The SQL statement to prepare and execute
-     * @param array         $values Values to bind to the statement
+     * @param ?array        $values Values to bind to the statement
      *
-     * @return \Generator
+     * @return Generator
      */
-    public function yieldPairs($stmt, array $values = null)
+    public function yieldPairs(Select|string $stmt, ?array $values = null): Generator
     {
         $sth = $this->prepexec($stmt, $values);
 
         $sth->setFetchMode(PDO::FETCH_NUM);
 
         foreach ($sth as $row) {
-            list($key, $value) = $row;
+            [$key, $value] = $row;
 
             yield $key => $value;
         }
@@ -382,8 +384,8 @@ public function yieldPairs($stmt, array $values = null)
     /**
      * Prepare and execute the given statement
      *
-     * @param Delete|Insert|Select|Update|string $stmt   The SQL statement to prepare and execute
-     * @param string|array                       $values Values to bind to the statement, if any
+     * @param Delete|Insert|Select|Update|string $stmt The SQL statement to prepare and execute
+     * @param string|array $values Values to bind to the statement, if any
      *
      * @return PDOStatement
      */
@@ -394,7 +396,7 @@ public function prepexec($stmt, $values = null)
         }
 
         if (is_object($stmt)) {
-            list($stmt, $values) = $this->getQueryBuilder()->assemble($stmt);
+            [$stmt, $values] = $this->getQueryBuilder()->assemble($stmt);
         }
 
         $this->connect();
@@ -412,9 +414,9 @@ public function prepexec($stmt, $values = null)
      *
      * @return PDOStatement
      */
-    public function select(Select $select)
+    public function select(Select $select): PDOStatement
     {
-        list($stmt, $values) = $this->getQueryBuilder()->assembleSelect($select);
+        [$stmt, $values] = $this->getQueryBuilder()->assembleSelect($select);
 
         return $this->prepexec($stmt, $values);
     }
@@ -422,7 +424,7 @@ public function select(Select $select)
     /**
      * Insert a table row with the specified data
      *
-     * @param string   $table The table to insert data into. The table specification must be in
+     * @param string $table The table to insert data into. The table specification must be in
      *                        one of the following formats: 'table' or 'schema.table'
      * @param iterable $data  Row data in terms of column-value pairs
      *
@@ -430,7 +432,7 @@ public function select(Select $select)
      *
      * @throws InvalidArgumentException If data type is invalid
      */
-    public function insert($table, $data)
+    public function insert(string $table, iterable $data): PDOStatement
     {
         $insert = (new Insert())
             ->into($table)
@@ -461,20 +463,24 @@ public function lastInsertId(?string $name = null): false|string
     /**
      * Update table rows with the specified data, optionally based on a given condition
      *
-     * @param string|array $table     The table to update. The table specification must be in one of
+     * @param array|string $table     The table to update. The table specification must be in one of
      *                                the following formats:
      *                                'table', 'table alias', ['alias' => 'table']
-     * @param iterable     $data      The columns to update in terms of column-value pairs
-     * @param mixed        $condition The WHERE condition
-     * @param string       $operator  The operator to combine multiple conditions with,
+     * @param iterable $data      The columns to update in terms of column-value pairs
+     * @param array|string|null $condition The WHERE condition
+     * @param string $operator  The operator to combine multiple conditions with,
      *                                if the condition is in the array format
      *
      * @return PDOStatement
      *
      * @throws InvalidArgumentException If data type is invalid
      */
-    public function update($table, $data, $condition = null, $operator = Sql::ALL)
-    {
+    public function update(
+        array|string $table,
+        iterable $data,
+        array|string|null $condition = null,
+        string $operator = Sql::ALL
+    ): PDOStatement {
         $update = (new Update())
             ->table($table)
             ->set($data);
@@ -489,16 +495,19 @@ public function update($table, $data, $condition = null, $operator = Sql::ALL)
     /**
      * Delete table rows, optionally based on a given condition
      *
-     * @param string|array $table     The table to delete data from. The table specification must be in one of the
+     * @param array|string $table     The table to delete data from. The table specification must be in one of the
      *                                following formats: 'table', 'table alias', ['alias' => 'table']
-     * @param mixed        $condition The WHERE condition
-     * @param string       $operator  The operator to combine multiple conditions with,
+     * @param array|string|null $condition The WHERE condition
+     * @param string $operator  The operator to combine multiple conditions with,
      *                                if the condition is in the array format
      *
      * @return PDOStatement
      */
-    public function delete($table, $condition = null, $operator = Sql::ALL)
-    {
+    public function delete(
+        array|string $table,
+        array|string|null $condition = null,
+        string $operator = Sql::ALL
+    ): PDOStatement {
         $delete = (new Delete())
             ->from($table);
 
@@ -514,7 +523,7 @@ public function delete($table, $condition = null, $operator = Sql::ALL)
      *
      * @return bool Whether the transaction was started successfully
      */
-    public function beginTransaction()
+    public function beginTransaction(): bool
     {
         $this->connect();
 
@@ -526,7 +535,7 @@ public function beginTransaction()
      *
      * @return bool Whether the transaction was committed successfully
      */
-    public function commitTransaction()
+    public function commitTransaction(): bool
     {
         return $this->pdo->commit();
     }
@@ -536,7 +545,7 @@ public function commitTransaction()
      *
      * @return bool Whether the transaction was rolled back successfully
      */
-    public function rollBackTransaction()
+    public function rollBackTransaction(): bool
     {
         return $this->pdo->rollBack();
     }
@@ -551,7 +560,7 @@ public function rollBackTransaction()
      *
      * @throws  Exception If an error occurs when running the callback
      */
-    public function transaction(callable $callback)
+    public function transaction(callable $callback): mixed
     {
         $this->beginTransaction();
 
@@ -567,8 +576,8 @@ public function transaction(callable $callback)
         return $result;
     }
 
-    public function quoteIdentifier($identifier)
+    public function quoteIdentifier(array|string $identifiers): string
     {
-        return $this->getAdapter()->quoteIdentifier($identifier);
+        return $this->getAdapter()->quoteIdentifier($identifiers);
     }
 }
diff --git a/src/Contract/Adapter.php b/src/Contract/Adapter.php
index 6142626..4be8ea7 100644
--- a/src/Contract/Adapter.php
+++ b/src/Contract/Adapter.php
@@ -15,7 +15,7 @@ interface Adapter extends Quoter
      *
      * @return string
      */
-    public function getDsn(Config $config);
+    public function getDsn(Config $config): string;
 
     /**
      * Get the PDO connect options based on the specified connection configuration
@@ -24,7 +24,7 @@ public function getDsn(Config $config);
      *
      * @return array
      */
-    public function getOptions(Config $config);
+    public function getOptions(Config $config): array;
 
     /**
      * Set the client time zone
@@ -33,7 +33,7 @@ public function getOptions(Config $config);
      *
      * @return $this
      */
-    public function setClientTimezone(Connection $db);
+    public function setClientTimezone(Connection $db): static;
 
     /**
      * Register callbacks for query builder events
@@ -42,5 +42,5 @@ public function setClientTimezone(Connection $db);
      *
      * @return $this
      */
-    public function registerQueryBuilderCallbacks(QueryBuilder $queryBuilder);
+    public function registerQueryBuilderCallbacks(QueryBuilder $queryBuilder): static;
 }
diff --git a/src/Contract/Quoter.php b/src/Contract/Quoter.php
index 79c4c78..08dda06 100644
--- a/src/Contract/Quoter.php
+++ b/src/Contract/Quoter.php
@@ -17,5 +17,5 @@ interface Quoter
      *
      * @return string
      */
-    public function quoteIdentifier($identifiers);
+    public function quoteIdentifier(array|string $identifiers): string;
 }
diff --git a/src/Cursor.php b/src/Cursor.php
index 85c5b1c..4df790a 100644
--- a/src/Cursor.php
+++ b/src/Cursor.php
@@ -12,13 +12,13 @@
 class Cursor implements IteratorAggregate, Paginatable
 {
     /** @var Connection */
-    protected $db;
+    protected Connection $db;
 
     /** @var Select */
-    protected $select;
+    protected Select $select;
 
     /** @var array */
-    protected $fetchModeAndArgs = [];
+    protected array $fetchModeAndArgs = [];
 
     /**
      * Create a new cursor for the given connection and query
@@ -37,7 +37,7 @@ public function __construct(Connection $db, Select $select)
      *
      * @return array
      */
-    public function getFetchMode()
+    public function getFetchMode(): array
     {
         return $this->fetchModeAndArgs;
     }
@@ -45,13 +45,13 @@ public function getFetchMode()
     /**
      * Set the fetch mode
      *
-     * @param int   $fetchMode Fetch mode as one of the PDO fetch mode constants.
+     * @param int $fetchMode Fetch mode as one of the PDO fetch mode constants.
      *                         Please see {@link https://www.php.net/manual/en/pdostatement.setfetchmode} for details
      * @param mixed ...$args   Fetch mode arguments
      *
      * @return $this
      */
-    public function setFetchMode($fetchMode, ...$args)
+    public function setFetchMode(int $fetchMode, ...$args): static
     {
         array_unshift($args, $fetchMode);
 
@@ -65,34 +65,34 @@ public function getIterator(): Traversable
         return $this->db->yieldAll($this->select, ...$this->getFetchMode());
     }
 
-    public function hasLimit()
+    public function hasLimit(): bool
     {
         return $this->select->hasLimit();
     }
 
-    public function getLimit()
+    public function getLimit(): ?int
     {
         return $this->select->getLimit();
     }
 
-    public function limit($limit)
+    public function limit(?int $limit): static
     {
         $this->select->limit($limit);
 
         return $this;
     }
 
-    public function hasOffset()
+    public function hasOffset(): bool
     {
         return $this->select->hasOffset();
     }
 
-    public function getOffset()
+    public function getOffset(): ?int
     {
         return $this->select->getOffset();
     }
 
-    public function offset($offset)
+    public function offset(?int $offset): static
     {
         $this->select->offset($offset);
 
diff --git a/src/Delete.php b/src/Delete.php
index 53736b8..15fb33f 100644
--- a/src/Delete.php
+++ b/src/Delete.php
@@ -10,15 +10,15 @@ class Delete implements CommonTableExpressionInterface, WhereInterface
     use CommonTableExpression;
     use Where;
 
-    /** @var array|null The FROM part of the DELETE query */
-    protected $from;
+    /** @var ?array The FROM part of the DELETE query */
+    protected ?array $from = null;
 
     /**
      * Get the FROM part of the DELETE query
      *
-     * @return array|null
+     * @return ?array
      */
-    public function getFrom()
+    public function getFrom(): ?array
     {
         return $this->from;
     }
@@ -32,12 +32,12 @@ public function getFrom()
      * If you are using special table names, e.g. reserved keywords for your DBMS, you are required to use
      * {@link Connection::quoteIdentifier()} as well.
      *
-     * @param string|array $table The table to delete data from. The table specification must be in one of the
+     * @param array|string $table The table to delete data from. The table specification must be in one of the
      *                            following formats: 'table', 'table alias', ['alias' => 'table']
      *
      * @return $this
      */
-    public function from($table)
+    public function from(array|string $table): static
     {
         $this->from = ! is_array($table) ? [$table] : $table;
 
diff --git a/src/Expression.php b/src/Expression.php
index 83c10bd..6edb266 100644
--- a/src/Expression.php
+++ b/src/Expression.php
@@ -8,46 +8,46 @@
 class Expression implements ExpressionInterface
 {
     /** @var string The statement of the expression */
-    protected $statement;
+    protected string $statement;
 
-    /** @var array The columns used by the expression */
-    protected $columns;
+    /** @var ?array The columns used by the expression */
+    protected ?array $columns;
 
     /** @var array The values for the expression */
-    protected $values;
+    protected array $values;
 
     /**
      * Create a new database expression
      *
      * @param string $statement The statement of the expression
-     * @param array $columns The columns used by the expression
+     * @param ?array $columns The columns used by the expression
      * @param mixed  ...$values The values for the expression
      */
-    public function __construct($statement, array $columns = null, ...$values)
+    public function __construct(string $statement, ?array $columns = null, ...$values)
     {
         $this->statement = $statement;
         $this->columns = $columns;
         $this->values = $values;
     }
 
-    public function getStatement()
+    public function getStatement(): string
     {
         return $this->statement;
     }
 
-    public function getColumns()
+    public function getColumns(): array
     {
         return $this->columns ?: [];
     }
 
-    public function setColumns(array $columns)
+    public function setColumns(array $columns): static
     {
         $this->columns = $columns;
 
         return $this;
     }
 
-    public function getValues()
+    public function getValues(): array
     {
         return $this->values;
     }
diff --git a/src/ExpressionInterface.php b/src/ExpressionInterface.php
index 9ebe5ee..9c994d6 100644
--- a/src/ExpressionInterface.php
+++ b/src/ExpressionInterface.php
@@ -12,14 +12,14 @@ interface ExpressionInterface
      *
      * @return string
      */
-    public function getStatement();
+    public function getStatement(): string;
 
     /**
      * Get the columns used by the expression
      *
      * @return array
      */
-    public function getColumns();
+    public function getColumns(): array;
 
     /**
      * Set the columns to use by the expression
@@ -28,12 +28,12 @@ public function getColumns();
      *
      * @return $this
      */
-    public function setColumns(array $columns);
+    public function setColumns(array $columns): static;
 
     /**
      * Get the values for the expression
      *
      * @return array
      */
-    public function getValues();
+    public function getValues(): array;
 }
diff --git a/src/Filter/In.php b/src/Filter/In.php
index c126af6..2c8ce84 100644
--- a/src/Filter/In.php
+++ b/src/Filter/In.php
@@ -7,18 +7,14 @@
 
 class In extends Filter\Condition
 {
-    use InAndNotInUtils;
-
     /**
      * Create a new sql IN condition
      *
      * @param string[]|string $column
      * @param Select $select
      */
-    public function __construct($column, Select $select)
+    public function __construct(array|string $column, Select $select)
     {
-        $this
-            ->setColumn($column)
-            ->setValue($select);
+        parent::__construct($column, $select);
     }
 }
diff --git a/src/Filter/InAndNotInUtils.php b/src/Filter/InAndNotInUtils.php
deleted file mode 100644
index 6f26de1..0000000
--- a/src/Filter/InAndNotInUtils.php
+++ /dev/null
@@ -1,62 +0,0 @@
-<?php
-
-namespace ipl\Sql\Filter;
-
-use ipl\Sql\Select;
-
-trait InAndNotInUtils
-{
-    /** @var string[]|string */
-    protected $column;
-
-    /** @var Select */
-    protected $value;
-
-    /**
-     * Get the columns of this condition
-     *
-     * @return string[]|string
-     */
-    public function getColumn()
-    {
-        return $this->column;
-    }
-
-    /**
-     * Set the columns of this condition
-     *
-     * @param string[]|string $column
-     *
-     * @return $this
-     */
-    public function setColumn($column): self
-    {
-        $this->column = $column;
-
-        return $this;
-    }
-
-    /**
-     * Get the value of this condition
-     *
-     * @return Select
-     */
-    public function getValue(): Select
-    {
-        return $this->value;
-    }
-
-    /**
-     * Set the value of this condition
-     *
-     * @param Select $value
-     *
-     * @return $this
-     */
-    public function setValue($value): self
-    {
-        $this->value = $value;
-
-        return $this;
-    }
-}
diff --git a/src/Filter/NotIn.php b/src/Filter/NotIn.php
index cdf6241..e42909f 100644
--- a/src/Filter/NotIn.php
+++ b/src/Filter/NotIn.php
@@ -7,18 +7,14 @@
 
 class NotIn extends Filter\Condition
 {
-    use InAndNotInUtils;
-
     /**
      * Create a new sql NOT IN condition
      *
      * @param string[]|string $column
      * @param Select $select
      */
-    public function __construct($column, Select $select)
+    public function __construct(array|string $column, Select $select)
     {
-        $this
-            ->setColumn($column)
-            ->setValue($select);
+        parent::__construct($column, $select);
     }
 }
diff --git a/src/Insert.php b/src/Insert.php
index 738a842..4ee0137 100644
--- a/src/Insert.php
+++ b/src/Insert.php
@@ -13,24 +13,24 @@ class Insert implements CommonTableExpressionInterface
 {
     use CommonTableExpression;
 
-    /** @var string|null The table for the INSERT INTO query */
-    protected $into;
+    /** @var ?string The table for the INSERT INTO query */
+    protected ?string $into = null;
 
-    /** @var array|null The columns for which the query provides values */
-    protected $columns;
+    /** @var ?array The columns for which the query provides values */
+    protected ?array $columns = null;
 
-    /** @var array|null The values to insert */
-    protected $values;
+    /** @var ?array $values The values to insert */
+    protected ?array $values = null;
 
-    /** @var Select|null The select query for INSERT INTO ... SELECT queries */
-    protected $select;
+    /** @var ?Select The select query for INSERT INTO ... SELECT queries */
+    protected ?Select $select = null;
 
     /**
      * Get the table for the INSERT INTo query
      *
-     * @return string|null
+     * @return ?string
      */
-    public function getInto()
+    public function getInto(): ?string
     {
         return $this->into;
     }
@@ -49,7 +49,7 @@ public function getInto()
      *
      * @return $this
      */
-    public function into($table)
+    public function into(string $table): static
     {
         $this->into = $table;
 
@@ -61,7 +61,7 @@ public function into($table)
      *
      * @return array
      */
-    public function getColumns()
+    public function getColumns(): array
     {
         if (! empty($this->columns)) {
             return array_keys($this->columns);
@@ -90,7 +90,7 @@ public function getColumns()
      *
      * @return $this
      */
-    public function columns(array $columns)
+    public function columns(array $columns): static
     {
         $this->columns = array_flip($columns);
 
@@ -102,7 +102,7 @@ public function columns(array $columns)
      *
      * @return array
      */
-    public function getValues()
+    public function getValues(): array
     {
         return array_values($this->values ?: []);
     }
@@ -135,7 +135,7 @@ public function values($values)
      *
      * @return $this
      */
-    public function select(Select $select)
+    public function select(Select $select): static
     {
         $this->select = $select;
 
@@ -145,9 +145,9 @@ public function select(Select $select)
     /**
      * Get the select query for the INSERT INTO ... SELECT statement
      *
-     * @return Select|null
+     * @return ?Select
      */
-    public function getSelect()
+    public function getSelect(): ?Select
     {
         return $this->select;
     }
diff --git a/src/LimitOffset.php b/src/LimitOffset.php
index 99c30a2..254314b 100644
--- a/src/LimitOffset.php
+++ b/src/LimitOffset.php
@@ -12,75 +12,61 @@ trait LimitOffset
      *
      * If unset or lower than 0, no limit will be applied.
      *
-     * @var int|null
+     * @var ?int
      */
-    protected $limit;
+    protected ?int $limit = null;
 
     /**
      * Offset from where to start the result set
      *
      * If unset or lower than 0, the result set will start from the beginning.
      *
-     * @var int|null
+     * @var ?int
      */
-    protected $offset;
+    protected ?int $offset = null;
 
-    public function hasLimit()
+    public function hasLimit(): bool
     {
         return $this->limit !== null;
     }
 
-    public function getLimit()
+    public function getLimit(): ?int
     {
         return $this->limit;
     }
 
-    public function limit($limit)
+    public function limit(?int $limit): static
     {
-        if ($limit !== null) {
-            $limit = (int) $limit;
-            if ($limit < 0) {
-                $limit = null;
-            }
-        }
-
-        $this->limit = $limit;
+        $this->limit = $limit < 0 ? null : $limit;
 
         return $this;
     }
 
-    public function resetLimit()
+    public function resetLimit(): static
     {
         $this->limit = null;
 
         return $this;
     }
 
-    public function hasOffset()
+    public function hasOffset(): bool
     {
         return $this->offset !== null;
     }
 
-    public function getOffset()
+    public function getOffset(): ?int
     {
         return $this->offset;
     }
 
-    public function offset($offset)
+    public function offset(?int $offset): static
     {
-        if ($offset !== null) {
-            $offset = (int) $offset;
-            if ($offset <= 0) {
-                $offset = null;
-            }
-        }
-
-        $this->offset = $offset;
+        $this->offset = $offset <= 0 ? null : $offset;
 
         return $this;
     }
 
-    public function resetOffset()
+    public function resetOffset(): static
     {
         $this->offset = null;
 
diff --git a/src/LimitOffsetInterface.php b/src/LimitOffsetInterface.php
index 94628c4..4dede24 100644
--- a/src/LimitOffsetInterface.php
+++ b/src/LimitOffsetInterface.php
@@ -12,60 +12,60 @@ interface LimitOffsetInterface
      *
      * @return bool
      */
-    public function hasLimit();
+    public function hasLimit(): bool;
 
     /**
      * Get the limit
      *
-     * @return int|null
+     * @return ?int
      */
-    public function getLimit();
+    public function getLimit(): ?int;
 
     /**
      * Set the limit
      *
-     * @param int|null $limit Maximum number of items to return.
+     * @param ?int $limit Maximum number of items to return.
      *                        If you want to disable the limit, use null or a negative value
      *
      * @return $this
      */
-    public function limit($limit);
+    public function limit(?int $limit): static;
 
     /**
      * Reset the limit
      *
      * @return $this
      */
-    public function resetLimit();
+    public function resetLimit(): static;
 
     /**
      * Get whether an offset is configured
      *
      * @return bool
      */
-    public function hasOffset();
+    public function hasOffset(): bool;
 
     /**
      * Get the offset
      *
-     * @return int|null
+     * @return ?int
      */
-    public function getOffset();
+    public function getOffset(): ?int;
 
     /**
      * Set the offset
      *
-     * @param int|null $offset Start result set after this many rows.
+     * @param ?int $offset Start result set after this many rows.
      *                         If you want to disable the offset, use null, 0, or a negative value
      *
      * @return $this
      */
-    public function offset($offset);
+    public function offset(?int $offset): static;
 
     /**
      * Reset the offset
      *
      * @return $this
      */
-    public function resetOffset();
+    public function resetOffset(): static;
 }
diff --git a/src/OrderBy.php b/src/OrderBy.php
index a19d7c5..822a8fa 100644
--- a/src/OrderBy.php
+++ b/src/OrderBy.php
@@ -8,19 +8,19 @@
 trait OrderBy
 {
     /** @var ?array ORDER BY part of the query */
-    protected $orderBy;
+    protected ?array $orderBy = null;
 
-    public function hasOrderBy()
+    public function hasOrderBy(): bool
     {
         return $this->orderBy !== null;
     }
 
-    public function getOrderBy()
+    public function getOrderBy(): ?array
     {
         return $this->orderBy;
     }
 
-    public function orderBy($orderBy, $direction = null)
+    public function orderBy($orderBy, int|string|null $direction = null): static
     {
         if (! is_array($orderBy)) {
             $orderBy = [$orderBy];
@@ -48,7 +48,7 @@ public function orderBy($orderBy, $direction = null)
         return $this;
     }
 
-    public function resetOrderBy()
+    public function resetOrderBy(): static
     {
         $this->orderBy = null;
 
@@ -60,7 +60,7 @@ public function resetOrderBy()
      *
      * Shall be called by using classes in their __clone()
      */
-    protected function cloneOrderBy()
+    protected function cloneOrderBy(): void
     {
         if ($this->orderBy !== null) {
             foreach ($this->orderBy as &$orderBy) {
diff --git a/src/OrderByInterface.php b/src/OrderByInterface.php
index 0ee0dda..37588df 100644
--- a/src/OrderByInterface.php
+++ b/src/OrderByInterface.php
@@ -12,14 +12,14 @@ interface OrderByInterface
      *
      * @return bool
      */
-    public function hasOrderBy();
+    public function hasOrderBy(): bool;
 
     /**
      * Get the ORDER BY part of the query
      *
-     * @return array|null
+     * @return ?array
      */
-    public function getOrderBy();
+    public function getOrderBy(): ?array;
 
     /**
      * Set the ORDER BY part of the query - either plain columns or expressions or scalar subqueries
@@ -33,19 +33,19 @@ public function getOrderBy();
      * If you are using special field names, e.g. reserved keywords for your DBMS, you are required to use
      * {@link Connection::quoteIdentifier()} as well.
      *
-     * @param string|int|array $orderBy   The ORDER BY part. The items can be in any format of the following:
+     * @param int|array|string $orderBy   The ORDER BY part. The items can be in any format of the following:
      *                                    ['column', 'column' => 'DESC', 'column' => SORT_DESC, ['column', 'DESC']]
-     * @param string|int   $direction     The default direction. Can be any of the following:
+     * @param int|string|null $direction     The default direction. Can be any of the following:
      *                                    'ASC', 'DESC', SORT_ASC, SORT_DESC
      *
      * @return $this
      */
-    public function orderBy($orderBy, $direction = null);
+    public function orderBy($orderBy, int|string|null $direction = null): static;
 
     /**
      * Reset the ORDER BY part of the query
      *
      * @return $this
      */
-    public function resetOrderBy();
+    public function resetOrderBy(): static;
 }
diff --git a/src/QueryBuilder.php b/src/QueryBuilder.php
index 07b5e3e..24f5e6f 100644
--- a/src/QueryBuilder.php
+++ b/src/QueryBuilder.php
@@ -2,13 +2,10 @@
 
 namespace ipl\Sql;
 
-use InvalidArgumentException;
 use ipl\Sql\Adapter\Mssql;
 use ipl\Sql\Contract\Adapter;
 use ipl\Stdlib\Events;
 
-use function ipl\Stdlib\get_php_type;
-
 class QueryBuilder
 {
     use Events;
@@ -141,9 +138,9 @@ class QueryBuilder
     public const ON_DELETE_ASSEMBLED = 'deleteAssembled';
 
     /** @var Adapter */
-    protected $adapter;
+    protected Adapter $adapter;
 
-    protected $separator = " ";
+    protected string $separator = " ";
 
     /**
      * Create a new query builder for the specified database adapter
@@ -163,26 +160,15 @@ public function __construct(Adapter $adapter)
      * @param Delete|Insert|Select|Update $stmt
      *
      * @return array
-     *
-     * @throw InvalidArgumentException If statement type is invalid
      */
-    public function assemble($stmt)
+    public function assemble(Select|Insert|Update|Delete $stmt): array
     {
-        switch (true) {
-            case $stmt instanceof Delete:
-                return $this->assembleDelete($stmt);
-            case $stmt instanceof Insert:
-                return $this->assembleInsert($stmt);
-            case $stmt instanceof Select:
-                return $this->assembleSelect($stmt);
-            case $stmt instanceof Update:
-                return $this->assembleUpdate($stmt);
-            default:
-                throw new InvalidArgumentException(sprintf(
-                    __METHOD__ . ' expects instances of Delete, Insert, Select or Update. Got %s instead.',
-                    get_php_type($stmt)
-                ));
-        }
+        return match (true) {
+            $stmt instanceof Delete => $this->assembleDelete($stmt),
+            $stmt instanceof Insert => $this->assembleInsert($stmt),
+            $stmt instanceof Select => $this->assembleSelect($stmt),
+            $stmt instanceof Update => $this->assembleUpdate($stmt)
+        };
     }
 
     /**
@@ -192,7 +178,7 @@ public function assemble($stmt)
      *
      * @return array
      */
-    public function assembleDelete(Delete $delete)
+    public function assembleDelete(Delete $delete): array
     {
         $values = [];
 
@@ -218,7 +204,7 @@ public function assembleDelete(Delete $delete)
      *
      * @return array
      */
-    public function assembleInsert(Insert $insert)
+    public function assembleInsert(Insert $insert): array
     {
         $values = [];
 
@@ -249,7 +235,7 @@ public function assembleInsert(Insert $insert)
      *
      * @return array
      */
-    public function assembleSelect(Select $select, array &$values = [])
+    public function assembleSelect(Select $select, array &$values = []): array
     {
         $select = clone $select;
 
@@ -271,7 +257,7 @@ public function assembleSelect(Select $select, array &$values = [])
 
         $unions = $this->buildUnions($select->getUnion(), $values);
         if ($unions) {
-            list($unionKeywords, $selects) = $unions;
+            [$unionKeywords, $selects] = $unions;
 
             if ($sql) {
                 $sql = "($sql)";
@@ -307,7 +293,7 @@ public function assembleSelect(Select $select, array &$values = [])
      *
      * @return array
      */
-    public function assembleUpdate(Update $update)
+    public function assembleUpdate(Update $update): array
     {
         $values = [];
 
@@ -335,7 +321,7 @@ public function assembleUpdate(Update $update)
      *
      * @return string The WITH part of a query
      */
-    public function buildWith(array $with, array &$values)
+    public function buildWith(array $with, array &$values): string
     {
         if (empty($with)) {
             return '';
@@ -345,8 +331,8 @@ public function buildWith(array $with, array &$values)
         $hasRecursive = false;
 
         foreach ($with as $cte) {
-            list($query, $alias, $recursive) = $cte;
-            list($cteSql, $cteValues) = $this->assembleSelect($query);
+            [$query, $alias, $recursive] = $cte;
+            [$cteSql, $cteValues] = $this->assembleSelect($query);
 
             $ctes[] = "$alias AS ($cteSql)";
 
@@ -360,11 +346,11 @@ public function buildWith(array $with, array &$values)
     /**
      * Build the DELETE FROM part of a query
      *
-     * @param array $from
+     * @param ?array $from
      *
      * @return string The DELETE FROM part of a query
      */
-    public function buildDeleteFrom(array $from = null)
+    public function buildDeleteFrom(?array $from = null): string
     {
         if ($from === null) {
             return '';
@@ -393,7 +379,7 @@ public function buildDeleteFrom(array $from = null)
      *
      * @return array
      */
-    public function unpackCondition($expression, array $values)
+    public function unpackCondition(string $expression, array $values): array
     {
         $placeholders = preg_match_all('/(\?)/', $expression, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER);
 
@@ -440,7 +426,7 @@ public function unpackCondition($expression, array $values)
      *
      * @return string
      */
-    public function buildCondition(array $condition, array &$values)
+    public function buildCondition(array $condition, array &$values): string
     {
         $sql = [];
 
@@ -486,12 +472,12 @@ public function buildCondition(array $condition, array &$values)
     /**
      * Build the WHERE part of a query
      *
-     * @param array $where
+     * @param ?array $where
      * @oaram array $values
      *
      * @return string The WHERE part of the query
      */
-    public function buildWhere(array $where = null, array &$values = [])
+    public function buildWhere(?array $where = null, array &$values = []): string
     {
         if ($where === null) {
             return '';
@@ -507,7 +493,7 @@ public function buildWhere(array $where = null, array &$values = [])
      *
      * @return string The INSERT INTO part of a INSERT INTO ... statement
      */
-    public function buildInsertInto($into)
+    public function buildInsertInto(?string $into): string
     {
         if (empty($into)) {
             return '';
@@ -525,7 +511,7 @@ public function buildInsertInto($into)
      *
      * @return string The columns and SELECT part of the INSERT INTO ... SELECT statement
      */
-    public function buildInsertIntoSelect(array $columns, Select $select, array &$values)
+    public function buildInsertIntoSelect(array $columns, Select $select, array &$values): string
     {
         $sql = [
             '(' . implode(',', $columns) . ')',
@@ -544,7 +530,7 @@ public function buildInsertIntoSelect(array $columns, Select $select, array &$va
      *
      * @return string The columns and values part of a INSERT INTO ... statement
      */
-    public function buildInsertColumnsAndValues(array $columns, array $insertValues, array &$values)
+    public function buildInsertColumnsAndValues(array $columns, array $insertValues, array &$values): string
     {
         $sql = ['(' . implode(',', $columns) . ')'];
 
@@ -570,12 +556,12 @@ public function buildInsertColumnsAndValues(array $columns, array $insertValues,
      * Build the SELECT part of a query
      *
      * @param array $columns
-     * @param bool  $distinct
+     * @param bool $distinct
      * @param array $values
      *
      * @return string The SELECT part of the query
      */
-    public function buildSelect(array $columns, $distinct, array &$values)
+    public function buildSelect(array $columns, bool $distinct, array &$values): string
     {
         if (empty($columns)) {
             return '';
@@ -609,12 +595,12 @@ public function buildSelect(array $columns, $distinct, array &$values)
     /**
      * Build the FROM part of a query
      *
-     * @param array $from
+     * @param ?array $from
      * @param array $values
      *
      * @return string The FROM part of the query
      */
-    public function buildFrom(array $from = null, array &$values = [])
+    public function buildFrom(?array $from = null, array &$values = []): string
     {
         if ($from === null) {
             return '';
@@ -640,12 +626,13 @@ public function buildFrom(array $from = null, array &$values = [])
     /**
      * Build the JOIN part(s) of a query
      *
-     * @param array $joins
+     * @param ?array $joins
+     *
      * @oaram array $values
      *
      * @return string The JOIN part(s) of the query
      */
-    public function buildJoin($joins, array &$values)
+    public function buildJoin(?array $joins, array &$values): string
     {
         if ($joins === null) {
             return '';
@@ -653,7 +640,7 @@ public function buildJoin($joins, array &$values)
 
         $sql = [];
         foreach ($joins as $join) {
-            list($joinType, $table, $condition) = $join;
+            [$joinType, $table, $condition] = $join;
 
             if (is_array($table)) {
                 $tableName = null;
@@ -686,12 +673,12 @@ public function buildJoin($joins, array &$values)
     /**
      * Build the GROUP BY part of a query
      *
-     * @param array $groupBy
+     * @param ?array $groupBy
      * @param array $values
      *
      * @return string The GROUP BY part of the query
      */
-    public function buildGroupBy(array $groupBy = null, array &$values = [])
+    public function buildGroupBy(?array $groupBy = null, array &$values = []): string
     {
         if ($groupBy === null) {
             return '';
@@ -711,12 +698,12 @@ public function buildGroupBy(array $groupBy = null, array &$values = [])
     /**
      * Build the HAVING part of a query
      *
-     * @param array $having
+     * @param ?array $having
      * @param array $values
      *
      * @return string The HAVING part of the query
      */
-    public function buildHaving(array $having = null, array &$values = [])
+    public function buildHaving(?array $having = null, array &$values = []): string
     {
         if ($having === null) {
             return '';
@@ -728,12 +715,12 @@ public function buildHaving(array $having = null, array &$values = [])
     /**
      * Build the ORDER BY part of a query
      *
-     * @param array $orderBy
+     * @param ?array $orderBy
      * @param array $values
      *
      * @return string The ORDER BY part of the query
      */
-    public function buildOrderBy(array $orderBy = null, array &$values = [])
+    public function buildOrderBy(?array $orderBy = null, array &$values = []): string
     {
         if ($orderBy === null) {
             return '';
@@ -742,7 +729,7 @@ public function buildOrderBy(array $orderBy = null, array &$values = [])
         $sql = [];
 
         foreach ($orderBy as $column) {
-            list($column, $direction) = $column;
+            [$column, $direction] = $column;
 
             if ($column instanceof ExpressionInterface) {
                 $column = $this->buildExpression($column, $values);
@@ -763,12 +750,12 @@ public function buildOrderBy(array $orderBy = null, array &$values = [])
     /**
      * Build the LIMIT and OFFSET part of a query
      *
-     * @param int $limit
-     * @param int $offset
+     * @param ?int $limit
+     * @param ?int $offset
      *
      * @return string The LIMIT and OFFSET part of the query
      */
-    public function buildLimitOffset($limit = null, $offset = null)
+    public function buildLimitOffset(?int $limit = null, ?int $offset = null): string
     {
         $sql = [];
 
@@ -798,12 +785,12 @@ public function buildLimitOffset($limit = null, $offset = null)
     /**
      * Build the UNION parts of a query
      *
-     * @param array $unions
+     * @param ?array $unions
      * @param array $values
      *
-     * @return array|null The UNION parts of the query
+     * @return ?array The UNION parts of the query
      */
-    public function buildUnions(array $unions = null, array &$values = [])
+    public function buildUnions(?array $unions = null, array &$values = []): ?array
     {
         if ($unions === null) {
             return null;
@@ -813,10 +800,10 @@ public function buildUnions(array $unions = null, array &$values = [])
         $selects = [];
 
         foreach ($unions as $union) {
-            list($select, $all) = $union;
+            [$select, $all] = $union;
 
             if ($select instanceof Select) {
-                list($select, $values) = $this->assembleSelect($select, $values);
+                [$select, $values] = $this->assembleSelect($select, $values);
             }
 
             $unionKeywords[] = ($all ? 'UNION ALL' : 'UNION');
@@ -829,11 +816,11 @@ public function buildUnions(array $unions = null, array &$values = [])
     /**
      * Build the UPDATE {table} part of a query
      *
-     * @param array $updateTable The table to UPDATE
+     * @param ?array $updateTable The table to UPDATE
      *
      * @return string The UPDATE {table} part of the query
      */
-    public function buildUpdateTable(array $updateTable = null)
+    public function buildUpdateTable(?array $updateTable = null): string
     {
         if ($updateTable === null) {
             return '';
@@ -857,12 +844,12 @@ public function buildUpdateTable(array $updateTable = null)
     /**
      * Build the SET part of a UPDATE query
      *
-     * @param array $set
+     * @param ?array $set
      * @param array $values
      *
      * @return string The SET part of a UPDATE query
      */
-    public function buildUpdateSet(array $set = null, array &$values = [])
+    public function buildUpdateSet(?array $set = null, array &$values = []): string
     {
         if (empty($set)) {
             return '';
@@ -892,7 +879,7 @@ public function buildUpdateSet(array $set = null, array &$values = [])
      *
      * @return string The expression's statement
      */
-    public function buildExpression(ExpressionInterface $expression, array &$values = [])
+    public function buildExpression(ExpressionInterface $expression, array &$values = []): string
     {
         $stmt = $expression->getStatement();
         $columns = $expression->getColumns();
diff --git a/src/Select.php b/src/Select.php
index f56a131..ecf3a62 100644
--- a/src/Select.php
+++ b/src/Select.php
@@ -13,13 +13,13 @@ class Select implements CommonTableExpressionInterface, LimitOffsetInterface, Or
     use Where;
 
     /** @var bool Whether the query is DISTINCT */
-    protected $distinct = false;
+    protected bool $distinct = false;
 
-    /** @var array|null The columns for the SELECT query */
-    protected $columns;
+    /** @var ?array The columns for the SELECT query */
+    protected ?array $columns = null;
 
-    /** @var array|null FROM part of the query, i.e. the table names to select data from */
-    protected $from;
+    /** @var ?array FROM part of the query, i.e. the table names to select data from */
+    protected ?array $from = null;
 
     /**
      * The tables to JOIN
@@ -31,13 +31,13 @@ class Select implements CommonTableExpressionInterface, LimitOffsetInterface, Or
      *
      * @var ?array
      */
-    protected $join;
+    protected ?array $join = null;
 
-    /** @var array|null The columns for the GROUP BY part of the query */
-    protected $groupBy;
+    /** @var ?array The columns for the GROUP BY part of the query */
+    protected ?array $groupBy = null;
 
-    /** @var array|null Internal representation for the HAVING part of the query */
-    protected $having;
+    /** @var ?array Internal representation for the HAVING part of the query */
+    protected ?array $having = null;
 
     /**
      * The queries to UNION
@@ -49,14 +49,14 @@ class Select implements CommonTableExpressionInterface, LimitOffsetInterface, Or
      *
      * @var ?array
      */
-    protected $union;
+    protected ?array $union = null;
 
     /**
      * Get whether to SELECT DISTINCT
      *
      * @return bool
      */
-    public function getDistinct()
+    public function getDistinct(): bool
     {
         return $this->distinct;
     }
@@ -68,7 +68,7 @@ public function getDistinct()
      *
      * @return $this
      */
-    public function distinct($distinct = true)
+    public function distinct(bool $distinct = true): static
     {
         $this->distinct = $distinct;
 
@@ -80,7 +80,7 @@ public function distinct($distinct = true)
      *
      * @return array
      */
-    public function getColumns()
+    public function getColumns(): array
     {
         return $this->columns ?: [];
     }
@@ -102,7 +102,7 @@ public function getColumns()
      *
      * @return $this
      */
-    public function columns($columns)
+    public function columns($columns): static
     {
         if (! is_array($columns)) {
             $columns = [$columns];
@@ -116,9 +116,9 @@ public function columns($columns)
     /**
      * Get the FROM part of the query
      *
-     * @return array|null
+     * @return ?array
      */
-    public function getFrom()
+    public function getFrom(): ?array
     {
         return $this->from;
     }
@@ -139,7 +139,7 @@ public function getFrom()
      *
      * @return $this
      */
-    public function from($tables)
+    public function from($tables): static
     {
         if (! is_array($tables)) {
             $tables = [$tables];
@@ -153,9 +153,9 @@ public function from($tables)
     /**
      * Get the JOIN part(s) of the query
      *
-     * @return array|null
+     * @return ?array
      */
-    public function getJoin()
+    public function getJoin(): ?array
     {
         return $this->join;
     }
@@ -174,7 +174,7 @@ public function getJoin()
      *
      * @return $this
      */
-    public function join($table, $condition, $operator = Sql::ALL)
+    public function join($table, $condition, $operator = Sql::ALL): static
     {
         $this->join[] = ['INNER', $table, $this->buildCondition($condition, $operator)];
 
@@ -195,7 +195,7 @@ public function join($table, $condition, $operator = Sql::ALL)
      *
      * @return $this
      */
-    public function joinLeft($table, $condition, $operator = Sql::ALL)
+    public function joinLeft($table, $condition, $operator = Sql::ALL): static
     {
         $this->join[] = ['LEFT', $table, $this->buildCondition($condition, $operator)];
 
@@ -216,7 +216,7 @@ public function joinLeft($table, $condition, $operator = Sql::ALL)
      *
      * @return $this
      */
-    public function joinRight($table, $condition, $operator = Sql::ALL)
+    public function joinRight($table, $condition, $operator = Sql::ALL): static
     {
         $this->join[] = ['RIGHT', $table, $this->buildCondition($condition, $operator)];
 
@@ -226,9 +226,9 @@ public function joinRight($table, $condition, $operator = Sql::ALL)
     /**
      * Get the GROUP BY part of the query
      *
-     * @return array|null
+     * @return ?array
      */
-    public function getGroupBy()
+    public function getGroupBy(): ?array
     {
         return $this->groupBy;
     }
@@ -249,7 +249,7 @@ public function getGroupBy()
      *
      * @return $this
      */
-    public function groupBy($groupBy)
+    public function groupBy($groupBy): static
     {
         $this->groupBy = array_merge(
             $this->groupBy === null ? [] : $this->groupBy,
@@ -262,9 +262,9 @@ public function groupBy($groupBy)
     /**
      * Get the HAVING part of the query
      *
-     * @return array|null
+     * @return ?array
      */
-    public function getHaving()
+    public function getHaving(): ?array
     {
         return $this->having;
     }
@@ -291,7 +291,7 @@ public function getHaving()
      *
      * @return $this
      */
-    public function having($condition, $operator = Sql::ALL)
+    public function having($condition, string $operator = Sql::ALL): static
     {
         $this->mergeCondition($this->having, $this->buildCondition($condition, $operator), Sql::ALL);
 
@@ -309,7 +309,7 @@ public function having($condition, $operator = Sql::ALL)
      *
      * @return $this
      */
-    public function orHaving($condition, $operator = Sql::ALL)
+    public function orHaving($condition, string $operator = Sql::ALL): static
     {
         $this->mergeCondition($this->having, $this->buildCondition($condition, $operator), Sql::ANY);
 
@@ -327,7 +327,7 @@ public function orHaving($condition, $operator = Sql::ALL)
      *
      * @return  $this
      */
-    public function notHaving($condition, $operator = Sql::ALL)
+    public function notHaving($condition, string $operator = Sql::ALL)
     {
         $this->mergeCondition($this->having, $this->buildCondition($condition, $operator), Sql::NOT_ALL);
 
@@ -345,7 +345,7 @@ public function notHaving($condition, $operator = Sql::ALL)
      *
      * @return $this
      */
-    public function orNotHaving($condition, $operator = Sql::ALL)
+    public function orNotHaving($condition, string $operator = Sql::ALL)
     {
         $this->mergeCondition($this->having, $this->buildCondition($condition, $operator), Sql::NOT_ANY);
 
@@ -355,9 +355,9 @@ public function orNotHaving($condition, $operator = Sql::ALL)
     /**
      * Get the UNION parts of the query
      *
-     * @return array|null
+     * @return ?array
      */
-    public function getUnion()
+    public function getUnion(): ?array
     {
         return $this->union;
     }
@@ -365,11 +365,11 @@ public function getUnion()
     /**
      * Combine a query with UNION
      *
-     * @param Select|string $query
+     * @param string|Select $query
      *
      * @return $this
      */
-    public function union($query)
+    public function union(Select|string $query): static
     {
         $this->union[] = [$query, false];
 
@@ -379,11 +379,11 @@ public function union($query)
     /**
      * Combine a query with UNION ALL
      *
-     * @param Select|string $query
+     * @param string|Select $query
      *
      * @return $this
      */
-    public function unionAll($query)
+    public function unionAll(Select|string $query): static
     {
         $this->union[] = [$query, true];
 
@@ -395,7 +395,7 @@ public function unionAll($query)
      *
      * @return $this
      */
-    public function resetDistinct()
+    public function resetDistinct(): static
     {
         $this->distinct = false;
 
@@ -407,7 +407,7 @@ public function resetDistinct()
      *
      * @return $this
      */
-    public function resetColumns()
+    public function resetColumns(): static
     {
         $this->columns = null;
 
@@ -419,7 +419,7 @@ public function resetColumns()
      *
      * @return $this
      */
-    public function resetFrom()
+    public function resetFrom(): static
     {
         $this->from = null;
 
@@ -431,7 +431,7 @@ public function resetFrom()
      *
      * @return $this
      */
-    public function resetJoin()
+    public function resetJoin(): static
     {
         $this->join = null;
 
@@ -443,7 +443,7 @@ public function resetJoin()
      *
      * @return $this
      */
-    public function resetGroupBy()
+    public function resetGroupBy(): static
     {
         $this->groupBy = null;
 
@@ -455,7 +455,7 @@ public function resetGroupBy()
      *
      * @return $this
      */
-    public function resetHaving()
+    public function resetHaving(): static
     {
         $this->having = null;
 
@@ -467,7 +467,7 @@ public function resetHaving()
      *
      * @return $this
      */
-    public function resetUnion()
+    public function resetUnion(): static
     {
         $this->union = null;
 
@@ -479,7 +479,7 @@ public function resetUnion()
      *
      * @return Select
      */
-    public function getCountQuery()
+    public function getCountQuery(): Select|static
     {
         $countQuery = clone $this;
 
diff --git a/src/Sql.php b/src/Sql.php
index 000a43a..bb90bff 100644
--- a/src/Sql.php
+++ b/src/Sql.php
@@ -33,7 +33,7 @@ class Sql
      *
      * @return Delete
      */
-    public static function delete()
+    public static function delete(): Delete
     {
         return new Delete();
     }
@@ -43,7 +43,7 @@ public static function delete()
      *
      * @return Insert
      */
-    public static function insert()
+    public static function insert(): Insert
     {
         return new Insert();
     }
@@ -53,7 +53,7 @@ public static function insert()
      *
      * @return Select
      */
-    public static function select()
+    public static function select(): Select
     {
         return new Select();
     }
@@ -63,7 +63,7 @@ public static function select()
      *
      * @return Update
      */
-    public static function update()
+    public static function update(): Update
     {
         return new Update();
     }
diff --git a/src/Test/SqlAssertions.php b/src/Test/SqlAssertions.php
index 74a04ba..62d4ab0 100644
--- a/src/Test/SqlAssertions.php
+++ b/src/Test/SqlAssertions.php
@@ -33,7 +33,7 @@ protected function setUpSqlAssertions(): void
      *
      * @return void
      */
-    public function assertSql(string $sql, $statement, array $values = null, string $message = ''): void
+    public function assertSql(string $sql, $statement, ?array $values = null, string $message = ''): void
     {
         // Reduce whitespaces to just one space
         $sql = preg_replace('/\s+/', ' ', trim($sql));
diff --git a/src/Test/TestConnection.php b/src/Test/TestConnection.php
index 913070f..1e149b8 100644
--- a/src/Test/TestConnection.php
+++ b/src/Test/TestConnection.php
@@ -14,22 +14,22 @@ public function __construct()
         $this->adapter = new TestAdapter();
     }
 
-    public function connect()
+    public function connect(): static
     {
         return $this;
     }
 
-    public function beginTransaction()
+    public function beginTransaction(): bool
     {
         throw new \LogicException('Transactions are not supported by the test connection');
     }
 
-    public function commitTransaction()
+    public function commitTransaction(): bool
     {
         throw new \LogicException('Transactions are not supported by the test connection');
     }
 
-    public function rollbackTransaction()
+    public function rollbackTransaction(): bool
     {
         throw new \LogicException('Transactions are not supported by the test connection');
     }
@@ -43,7 +43,7 @@ public function getIterator(): \Iterator
                     return new \ArrayIterator([]);
                 }
 
-                public function setFetchMode($mode, ...$args): bool
+                public function setFetchMode($mode, ...$args): true
                 {
                     return true;
                 }
@@ -55,7 +55,7 @@ public function getIterator(): \Iterator
                     return new \ArrayIterator([]);
                 }
 
-                public function setFetchMode($mode, $params = null): bool
+                public function setFetchMode($mode, ...$params): true
                 {
                     return true;
                 }
diff --git a/src/Update.php b/src/Update.php
index 356a610..af9ad53 100644
--- a/src/Update.php
+++ b/src/Update.php
@@ -14,18 +14,18 @@ class Update implements CommonTableExpressionInterface, WhereInterface
     use CommonTableExpression;
     use Where;
 
-    /** @var array|null The table for the UPDATE query */
-    protected $table;
+    /** @var ?array The table for the UPDATE query */
+    protected ?array $table = null;
 
-    /** @var array|null The columns to update in terms of column-value pairs */
-    protected $set = [];
+    /** @var ?array The columns to update in terms of column-value pairs */
+    protected ?array $set = [];
 
     /**
      * Get the table for the UPDATE query
      *
-     * @return array|null
+     * @return ?array
      */
-    public function getTable()
+    public function getTable(): ?array
     {
         return $this->table;
     }
@@ -39,12 +39,12 @@ public function getTable()
      * If you are using special table names, e.g. reserved keywords for your DBMS, you are required to use
      * {@link Connection::quoteIdentifier()} as well.
      *
-     * @param string|array $table The table to update. The table specification must be in one of the
+     * @param array|string $table The table to update. The table specification must be in one of the
      *                            following formats: 'table', 'table alias', ['alias' => 'table']
      *
      * @return $this
      */
-    public function table($table)
+    public function table(array|string $table): static
     {
         $this->table = is_array($table) ? $table : [$table];
 
@@ -54,9 +54,9 @@ public function table($table)
     /**
      * Get the columns to update in terms of column-value pairs
      *
-     * @return array|null
+     * @return ?array
      */
-    public function getSet()
+    public function getSet(): ?array
     {
         return $this->set;
     }
@@ -78,7 +78,7 @@ public function getSet()
      *
      * @throws InvalidArgumentException If set type is invalid
      */
-    public function set($set)
+    public function set($set): static
     {
         $this->set = arrayval($set);
 
diff --git a/src/Where.php b/src/Where.php
index f862846..404766c 100644
--- a/src/Where.php
+++ b/src/Where.php
@@ -7,47 +7,47 @@
  */
 trait Where
 {
-    /** @var array|null Internal representation for the WHERE part of the query */
-    protected $where;
+    /** @var ?array Internal representation for the WHERE part of the query */
+    protected ?array $where = null;
 
-    public function getWhere()
+    public function getWhere(): ?array
     {
         return $this->where;
     }
 
-    public function where($condition, ...$args)
+    public function where($condition, ...$args): static
     {
-        list($condition, $operator) = $this->prepareConditionArguments($condition, $args);
+        [$condition, $operator] = $this->prepareConditionArguments($condition, $args);
         $this->mergeCondition($this->where, $this->buildCondition($condition, $operator), Sql::ALL);
 
         return $this;
     }
 
-    public function orWhere($condition, ...$args)
+    public function orWhere($condition, ...$args): static
     {
-        list($condition, $operator) = $this->prepareConditionArguments($condition, $args);
+        [$condition, $operator] = $this->prepareConditionArguments($condition, $args);
         $this->mergeCondition($this->where, $this->buildCondition($condition, $operator), Sql::ANY);
 
         return $this;
     }
 
-    public function notWhere($condition, ...$args)
+    public function notWhere($condition, ...$args): static
     {
-        list($condition, $operator) = $this->prepareConditionArguments($condition, $args);
+        [$condition, $operator] = $this->prepareConditionArguments($condition, $args);
         $this->mergeCondition($this->where, $this->buildCondition($condition, $operator), Sql::NOT_ALL);
 
         return $this;
     }
 
-    public function orNotWhere($condition, ...$args)
+    public function orNotWhere($condition, ...$args): static
     {
-        list($condition, $operator) = $this->prepareConditionArguments($condition, $args);
+        [$condition, $operator] = $this->prepareConditionArguments($condition, $args);
         $this->mergeCondition($this->where, $this->buildCondition($condition, $operator), Sql::NOT_ANY);
 
         return $this;
     }
 
-    public function resetWhere()
+    public function resetWhere(): static
     {
         $this->where = null;
 
@@ -64,7 +64,7 @@ public function resetWhere()
      *
      * @return array
      */
-    protected function buildCondition($condition, $operator)
+    protected function buildCondition($condition, string $operator): array
     {
         if (is_array($condition)) {
             if (empty($condition)) {
@@ -86,7 +86,7 @@ protected function buildCondition($condition, $operator)
      * @param array  $condition As returned by {@link buildCondition()}
      * @param string $operator
      */
-    protected function mergeCondition(&$base, array $condition, $operator)
+    protected function mergeCondition(&$base, array $condition, string $operator): void
     {
         if ($base === null) {
             $base = [$operator, [$condition]];
@@ -111,7 +111,7 @@ protected function mergeCondition(&$base, array $condition, $operator)
      *
      * @return array
      */
-    protected function prepareConditionArguments($condition, array $args)
+    protected function prepareConditionArguments($condition, array $args): array
     {
         // Default operator
         $operator = Sql::ALL;
@@ -132,7 +132,7 @@ protected function prepareConditionArguments($condition, array $args)
      *
      * Shall be called by using classes in their __clone()
      */
-    protected function cloneWhere()
+    protected function cloneWhere(): void
     {
         if ($this->where !== null) {
             $this->cloneCondition($this->where);
@@ -144,7 +144,7 @@ protected function cloneWhere()
      *
      * @param array $condition As returned by {@link buildCondition()}
      */
-    protected function cloneCondition(array &$condition)
+    protected function cloneCondition(array &$condition): void
     {
         foreach ($condition as &$subCondition) {
             if (is_array($subCondition)) {
diff --git a/src/WhereInterface.php b/src/WhereInterface.php
index e724465..a74a8dc 100644
--- a/src/WhereInterface.php
+++ b/src/WhereInterface.php
@@ -10,9 +10,9 @@ interface WhereInterface
     /**
      * Get the WHERE part of the query
      *
-     * @return array|null
+     * @return ?array
      */
-    public function getWhere();
+    public function getWhere(): ?array;
 
     /**
      * Add a WHERE part of the query
@@ -37,7 +37,7 @@ public function getWhere();
      *
      * @return $this
      */
-    public function where($condition, ...$args);
+    public function where($condition, ...$args): static;
 
     /**
      * Add a OR part to the WHERE part of the query
@@ -49,7 +49,7 @@ public function where($condition, ...$args);
      *
      * @return $this
      */
-    public function orWhere($condition, ...$args);
+    public function orWhere($condition, ...$args): static;
 
     /**
      * Add a AND NOT part to the WHERE part of the query
@@ -61,7 +61,7 @@ public function orWhere($condition, ...$args);
      *
      * @return $this
      */
-    public function notWhere($condition, ...$args);
+    public function notWhere($condition, ...$args): static;
 
     /**
      * Add a OR NOT part to the WHERE part of the query
@@ -73,12 +73,12 @@ public function notWhere($condition, ...$args);
      *
      * @return $this
      */
-    public function orNotWhere($condition, ...$args);
+    public function orNotWhere($condition, ...$args): static;
 
     /**
      * Reset the WHERE part of the query
      *
      * @return $this
      */
-    public function resetWhere();
+    public function resetWhere(): static;
 }
diff --git a/tests/ConfigTest.php b/tests/ConfigTest.php
index 58d0324..4f3183e 100644
--- a/tests/ConfigTest.php
+++ b/tests/ConfigTest.php
@@ -52,7 +52,7 @@ public function testAllPropertiesCanBeSet(): void
             'password'                      => 'test_password',
             'use_ssl'                       => 'true',
             'charset'                       => 'latin1',
-            'options'                       => 'test_options',
+            'options'                       => ['test_options'],
             'ssl_key'                       => 'test_ssl_key',
             'ssl_cert'                      => 'test_ssl_cert',
             'ssl_ca'                        => 'test_ssl_ca',
@@ -69,7 +69,7 @@ public function testAllPropertiesCanBeSet(): void
         $this->assertSame($config->password, 'test_password');
         $this->assertSame($config->useSsl, 'true');
         $this->assertSame($config->charset, 'latin1');
-        $this->assertSame($config->options, 'test_options');
+        $this->assertSame($config->options, ['test_options']);
         $this->assertSame($config->sslKey, 'test_ssl_key');
         $this->assertSame($config->sslCert, 'test_ssl_cert');
         $this->assertSame($config->sslCa, 'test_ssl_ca');