diff --git a/lib/Adapter/MysqlAdapter.php b/lib/Adapter/MysqlAdapter.php
index ea90b220..11758da9 100644
--- a/lib/Adapter/MysqlAdapter.php
+++ b/lib/Adapter/MysqlAdapter.php
@@ -41,7 +41,7 @@ public function query_for_tables(): \PDOStatement
     public function create_column(array $column): Column
     {
         $c = new Column();
-        $c->inflected_name    = Inflector::instance()->variablize($column['field']);
+        $c->inflected_name    = Inflector::variablize($column['field']);
         $c->name            = $column['field'];
         $c->nullable        = ('YES' === $column['null'] ? true : false);
         $c->pk                = ('PRI' === $column['key'] ? true : false);
@@ -84,7 +84,7 @@ public function accepts_limit_and_order_for_update_and_delete(): bool
     }
 
     /**
-     * @return array<string, array<string, mixed>>
+     * @return array<string, string|array<string, mixed>>
      */
     public function native_database_types(): array
     {
diff --git a/lib/Adapter/PgsqlAdapter.php b/lib/Adapter/PgsqlAdapter.php
index 3a9aaaea..9c72baa0 100644
--- a/lib/Adapter/PgsqlAdapter.php
+++ b/lib/Adapter/PgsqlAdapter.php
@@ -85,7 +85,7 @@ public function query_for_tables(): \PDOStatement
     public function create_column(array $column): Column
     {
         $c = new Column();
-        $c->inflected_name    = Inflector::instance()->variablize($column['field']);
+        $c->inflected_name    = Inflector::variablize($column['field']);
         $c->name            = $column['field'];
         $c->nullable        = ($column['not_nullable'] ? false : true);
         $c->pk                = ($column['pk'] ? true : false);
diff --git a/lib/Adapter/SqliteAdapter.php b/lib/Adapter/SqliteAdapter.php
index 128580b5..b23be72c 100644
--- a/lib/Adapter/SqliteAdapter.php
+++ b/lib/Adapter/SqliteAdapter.php
@@ -19,14 +19,14 @@
  */
 class SqliteAdapter extends Connection
 {
-    public static $datetime_format = 'Y-m-d H:i:s';
+    public static string $datetime_format = 'Y-m-d H:i:s';
 
-    protected function __construct(\stdClass $info)
+    protected function __construct(array $info)
     {
-        if (!file_exists($info->host)) {
-            throw new ConnectionException("Could not find sqlite db: $info->host");
+        if (!file_exists($info['host'])) {
+            throw new ConnectionException('Could not find sqlite db: ' . $info['host']);
         }
-        $this->connection = new \PDO("sqlite:$info->host", null, null, static::$PDO_OPTIONS);
+        $this->connection = new \PDO('sqlite:' . $info['host'], null, null, static::$PDO_OPTIONS);
     }
 
     public function limit(string $sql, int $offset = 0, int $limit = 0)
@@ -49,10 +49,10 @@ public function query_for_tables(): \PDOStatement
     public function create_column(array $column): Column
     {
         $c = new Column();
-        $c->inflected_name  = Inflector::instance()->variablize($column['name']);
+        $c->inflected_name  = Inflector::variablize($column['name']);
         $c->name            = $column['name'];
-        $c->nullable        = $column['notnull'] ? false : true;
-        $c->pk              = $column['pk'] ? true : false;
+        $c->nullable        = !$column['notnull'];
+        $c->pk              = (bool) $column['pk'];
         $c->auto_increment  = in_array(
             strtoupper($column['type']),
             ['INT', 'INTEGER']
diff --git a/lib/Cache.php b/lib/Cache.php
index b96fd04a..832ef33e 100644
--- a/lib/Cache.php
+++ b/lib/Cache.php
@@ -54,10 +54,16 @@ public static function initialize(string $url = '', array $options = []): void
     {
         if ($url) {
             $url = parse_url($url);
-            $file = ucwords(Inflector::instance()->camelize($url['scheme']));
+            assert(is_array($url));
+            $file = ucwords(Inflector::camelize($url['scheme'] ?? ''));
             $class = "ActiveRecord\\$file";
             require_once __DIR__ . "/cache/$file.php";
-            static::$adapter = new $class($url);
+
+            $cache = new $class($url);
+
+            assert($cache instanceof Memcache);
+
+            static::$adapter  = $cache;
         } else {
             static::$adapter = null;
         }
@@ -85,7 +91,7 @@ public static function get(string $key, \Closure $closure, int $expire = null):
         $key = static::get_namespace() . $key;
 
         if (!($value = static::$adapter->read($key))) {
-            static::$adapter->write($key, $value = $closure(), $expire ?? static::$options['expire']);
+            static::$adapter->write($key, $value = $closure(), $expire ?? static::$options['expire'] ?? 0);
         }
 
         return $value;
@@ -97,13 +103,9 @@ public static function set(string $key, mixed $var, int $expire = null): void
             return;
         }
 
-        if (is_null($expire)) {
-            $expire = static::$options['expire'];
-        }
-
         $key = static::get_namespace() . $key;
 
-        static::$adapter->write($key, $var, $expire);
+        static::$adapter->write($key, $var, $expire ?? static::$options['expire'] ?? 0);
     }
 
     public static function delete(string $key): void
diff --git a/lib/CallBack.php b/lib/CallBack.php
index 3826cdca..a611bf4a 100644
--- a/lib/CallBack.php
+++ b/lib/CallBack.php
@@ -102,7 +102,7 @@ class CallBack
     /**
      * Holds data for registered callbacks.
      *
-     * @var array<string, CallBack>
+     * @var array<string, array<\Closure|string>>
      */
     private array $registry = [];
 
@@ -141,7 +141,7 @@ public function __construct(string $model_class_name)
      *
      * @param $name string Name of a callback (see {@link VALID_CALLBACKS $VALID_CALLBACKS})
      *
-     * @return array<CallBack> array of callbacks or null if invalid callback name
+     * @return array<\Closure|string> array of callbacks or empty array if invalid callback name
      */
     public function get_callbacks(string $name): array
     {
diff --git a/lib/Column.php b/lib/Column.php
index 2555757e..1eaecf68 100644
--- a/lib/Column.php
+++ b/lib/Column.php
@@ -130,7 +130,7 @@ public static function castIntegerSafely($value): string|int
         }
 
         // It's just a decimal number
-        elseif (is_numeric($value) && floor($value) != $value) {
+        elseif (is_float($value) && floor($value) != $value) {
             return (int) $value;
         }
 
diff --git a/lib/Connection.php b/lib/Connection.php
index 43236327..7411eb4f 100644
--- a/lib/Connection.php
+++ b/lib/Connection.php
@@ -13,11 +13,20 @@
 use ActiveRecord\Exception\DatabaseException;
 use Closure;
 use PDO;
+use Psr\Log\LoggerInterface;
 
 /**
  * The base class for database connection adapters.
  *
- * @package ActiveRecord
+ * @phpstan-type ConnectionInfo array{
+ *     protocol: string,
+ *     host: string,
+ *     db: string|null,
+ *     user: string|null,
+ *     pass: string|null,
+ *     port?: int|null,
+ *     charset?: string|null
+ * }
  */
 abstract class Connection
 {
@@ -42,22 +51,16 @@ abstract class Connection
     public string $last_query;
     /**
      * Switch for logging.
-     *
-     * @var bool
      */
-    private $logging = false;
+    private bool $logging = false;
     /**
      * Contains a Logger object that must implement a log() method.
-     *
-     * @var object
      */
-    private $logger;
+    private LoggerInterface $logger;
     /**
      * The name of the protocol that is used.
-     *
-     * @var string
      */
-    public $protocol;
+    public string $protocol;
     /**
      * Database's date format
      *
@@ -66,10 +69,8 @@ abstract class Connection
     public static $date_format = 'Y-m-d';
     /**
      * Database's datetime format
-     *
-     * @var string
      */
-    public static $datetime_format = 'Y-m-d H:i:s';
+    public static string $datetime_format = 'Y-m-d H:i:s';
     /**
      * Default PDO options to set for each connection.
      *
@@ -126,16 +127,17 @@ public static function instance(string $connection_string_or_connection_name = n
             throw new DatabaseException('Empty connection string');
         }
         $info = static::parse_connection_url($connection_string);
-        $fqclass = static::load_adapter_class($info->protocol);
+        $fqclass = static::load_adapter_class($info['protocol']);
 
         try {
             $connection = new $fqclass($info);
-            $connection->protocol = $info->protocol;
+            assert($connection instanceof Connection);
+            $connection->protocol = $info['protocol'];
             $connection->logging = $config->get_logging();
             $connection->logger = $connection->logging ? $config->get_logger() : null;
 
-            if (isset($info->charset)) {
-                $connection->set_encoding($info->charset);
+            if (isset($info['charset'])) {
+                $connection->set_encoding($info['charset']);
             }
         } catch (\PDOException $e) {
             throw new DatabaseException($e);
@@ -162,6 +164,8 @@ protected static function load_adapter_class(string $adapter)
         }
         require_once $source;
 
+        assert(class_exists($fqclass));
+
         return $fqclass;
     }
 
@@ -186,26 +190,26 @@ protected static function load_adapter_class(string $adapter)
      *
      * @param string $connection_url A connection URL
      *
-     * @return object the parsed URL as an object
+     * @return ConnectionInfo
      */
-    public static function parse_connection_url(string $connection_url)
+    public static function parse_connection_url(string $connection_url): array
     {
         $url = @parse_url($connection_url);
 
         if (!isset($url['host'])) {
             throw new DatabaseException('Database host must be specified in the connection string. If you want to specify an absolute filename, use e.g. sqlite://unix(/path/to/file)');
         }
-        $info = new \stdClass();
-        $info->protocol = $url['scheme'];
-        $info->host = $url['host'];
-        $info->db = isset($url['path']) ? substr($url['path'], 1) : null;
-        $info->user = isset($url['user']) ? $url['user'] : null;
-        $info->pass = isset($url['pass']) ? $url['pass'] : null;
+        $host = $url['host'];
+        $db = isset($url['path']) ? substr($url['path'], 1) : null;
+        $user = $url['user'] ?? null;
+        $pass = $url['pass'] ?? null;
+        $protocol = $url['scheme'] ?? null;
+        $charset = null;
 
-        $allow_blank_db = ('sqlite' == $info->protocol);
+        $allow_blank_db = ('sqlite' == $protocol);
 
-        if ('unix(' == $info->host) {
-            $socket_database = $info->host . '/' . $info->db;
+        if ('unix(' == $host) {
+            $socket_database = $host . '/' . $db;
 
             if ($allow_blank_db) {
                 $unix_regex = '/^unix\((.+)\)\/?().*$/';
@@ -214,29 +218,25 @@ public static function parse_connection_url(string $connection_url)
             }
 
             if (preg_match_all($unix_regex, $socket_database, $matches) > 0) {
-                $info->host = $matches[1][0];
-                $info->db = $matches[2][0];
+                $host = $matches[1][0];
+                $db = $matches[2][0];
             }
-        } elseif ('windows(' == substr($info->host, 0, 8)) {
-            $info->host = urldecode(substr($info->host, 8) . '/' . substr($info->db, 0, -1));
-            $info->db = null;
-        }
-
-        if ($allow_blank_db && $info->db) {
-            $info->host .= '/' . $info->db;
+        } elseif ('windows(' == substr($host, 0, 8)) {
+            $host = urldecode(substr($host, 8) . '/' . substr($db, 0, -1));
+            $db = null;
         }
 
-        if (isset($url['port'])) {
-            $info->port = $url['port'];
+        if ($allow_blank_db && $db) {
+            $host .= '/' . $db;
         }
 
         if (false !== strpos($connection_url, 'decode=true')) {
-            if ($info->user) {
-                $info->user = urldecode($info->user);
+            if ($user) {
+                $user = urldecode($user);
             }
 
-            if ($info->pass) {
-                $info->pass = urldecode($info->pass);
+            if ($pass) {
+                $pass = urldecode($pass);
             }
         }
 
@@ -245,33 +245,45 @@ public static function parse_connection_url(string $connection_url)
                 list($name, $value) = explode('=', $pair);
 
                 if ('charset' == $name) {
-                    $info->charset = $value;
+                    $charset = $value;
                 }
             }
         }
 
-        return $info;
+        assert(!is_null($protocol));
+
+        return [
+            'charset' => $charset,
+            'protocol' => $protocol,
+            'host' => $host,
+            'db' => $db,
+            'user' => $user,
+            'pass' => $pass,
+            'port' => $url['port'] ?? null
+        ];
     }
 
     /**
      * Class Connection is a singleton. Access it via instance().
+     *
+     * @param ConnectionInfo $info
      */
-    protected function __construct(\stdClass $info)
+    protected function __construct(array $info)
     {
         try {
             // unix sockets start with a /
-            if ('/' != $info->host[0]) {
-                $host = "host=$info->host";
+            if ('/' != $info['host'][0]) {
+                $host = 'host=' . $info['host'];
 
-                if (isset($info->port)) {
-                    $host .= ";port=$info->port";
+                if (isset($info['port'])) {
+                    $host .= ';port=' . $info['port'];
                 }
             } else {
-                $host = "unix_socket=$info->host";
+                $host = 'unix_socket=' . $info['host'];
             }
 
-            $dsn = "$info->protocol:$host;dbname=$info->db";
-            $this->connection = new \PDO($dsn, $info->user, $info->pass, static::$PDO_OPTIONS);
+            $dsn = $info['protocol'] . ":$host;dbname=" . $info['db'];
+            $this->connection = new \PDO($dsn, $info['user'], $info['pass'], static::$PDO_OPTIONS);
         } catch (\PDOException $e) {
             throw new Exception\ConnectionException($e);
         }
@@ -484,26 +496,15 @@ public function quote_name($string)
             $string : static::$QUOTE_CHARACTER . $string . static::$QUOTE_CHARACTER;
     }
 
-    /**
-     * Return a date time formatted into the database's date format.
-     *
-     * @param DateTime $datetime The DateTime object
-     *
-     * @return string
-     */
-    public function date_to_string($datetime)
+    public function date_string(\DateTimeInterface $datetime): string
     {
         return $datetime->format(static::$date_format);
     }
 
     /**
      * Return a date time formatted into the database's datetime format.
-     *
-     * @param DateTime $datetime The DateTime object
-     *
-     * @return string
      */
-    public function datetime_to_string(\DateTime $datetime)
+    public function datetime_string(\DateTimeInterface $datetime): string
     {
         return $datetime->format(static::$datetime_format);
     }
@@ -524,6 +525,8 @@ public function string_to_datetime(string $string): ?DateTime
             return null;
         }
 
+        assert($date instanceof \DateTime);
+
         $date_class = Config::instance()->get_date_class();
 
         return $date_class::createFromFormat(
diff --git a/lib/Inflector.php b/lib/Inflector.php
index 7394d3f7..f394da7d 100644
--- a/lib/Inflector.php
+++ b/lib/Inflector.php
@@ -10,24 +10,10 @@
  */
 abstract class Inflector
 {
-    /**
-     * Get an instance of the {@link Inflector} class.
-     *
-     * @return object
-     */
-    public static function instance()
-    {
-        return new StandardInflector();
-    }
-
     /**
      * Turn a string into its camelized version.
-     *
-     * @param string $s string to convert
-     *
-     * @return string
      */
-    public function camelize($s)
+    public static function camelize(string $s): string
     {
         $s = preg_replace('/[_-]+/', '_', trim($s));
         $s = str_replace(' ', '_', $s);
@@ -53,12 +39,8 @@ public function camelize($s)
 
     /**
      * Determines if a string contains all uppercase characters.
-     *
-     * @param string $s string to check
-     *
-     * @return bool
      */
-    public static function is_upper($s)
+    public static function is_upper(string $s): bool
     {
         return strtoupper($s) === $s;
     }
@@ -66,12 +48,12 @@ public static function is_upper($s)
     /**
      * Convert a camelized string to a lowercase, underscored string.
      */
-    public function uncamelize(string $s): string
+    public static function uncamelize(string $s): string
     {
         $normalized = '';
 
         for ($i = 0, $n = strlen($s); $i < $n; ++$i) {
-            if (ctype_alpha($s[$i]) && self::is_upper($s[$i])) {
+            if (ctype_alpha($s[$i]) && static::is_upper($s[$i])) {
                 $normalized .= '_' . strtolower($s[$i]);
             } else {
                 $normalized .= $s[$i];
@@ -84,7 +66,7 @@ public function uncamelize(string $s): string
     /**
      * Convert a string with space into a underscored equivalent.
      */
-    public function underscorify(string $s): string
+    public static function underscorify(string $s): string
     {
         $res = preg_replace(['/[_\- ]+/', '/([a-z])([A-Z])/'], ['_', '\\1_\\2'], trim($s));
         assert(is_string($res));
@@ -92,25 +74,17 @@ public function underscorify(string $s): string
         return $res;
     }
 
-    public function keyify(string $class_name): string
+    public static function keyify(string $class_name): string
     {
-        return strtolower($this->underscorify(denamespace($class_name))) . '_id';
+        return strtolower(static::underscorify(denamespace($class_name))) . '_id';
     }
 
-    abstract public function variablize(string $s): string;
-}
-
-/**
- * @package ActiveRecord
- */
-class StandardInflector extends Inflector
-{
-    public function tableize(string $s): string
+    public static function tableize(string $s): string
     {
-        return Utils::pluralize(strtolower($this->underscorify($s)));
+        return Utils::pluralize(strtolower(static::underscorify($s)));
     }
 
-    public function variablize(string $s): string
+    public static function variablize(string $s): string
     {
         return str_replace(['-', ' '], ['_', '_'], strtolower(trim($s)));
     }
diff --git a/lib/Model.php b/lib/Model.php
index bde26f2e..51a53559 100644
--- a/lib/Model.php
+++ b/lib/Model.php
@@ -139,7 +139,7 @@ class Model
     /**
      * Array of relationship objects as model_attribute_name => relationship
      *
-     * @var array<class-string,Model>
+     * @var array<string,Model|array<Model>>
      */
     private array $__relationships = [];
 
@@ -184,7 +184,7 @@ class Model
     /**
      * Set this to specify an expiration period for this model. If not set, the expire value you set in your cache options will be used.
      *
-     * @var number
+     * @var int
      */
     public static $cache_expire;
 
@@ -410,7 +410,9 @@ public function &__get($name)
         $name = strtolower($name);
         if (method_exists($this, "get_$name")) {
             $name = "get_$name";
-            $res = call_user_func([$this, $name]);
+            $callable = [$this, $name];
+            assert(is_callable($callable));
+            $res = call_user_func($callable);
 
             return $res;
         }
@@ -519,12 +521,15 @@ public function __set(string $name, mixed $value): void
         }
 
         if ('id' == $name) {
-            $this->assign_attribute($this->get_primary_key(true), $value);
+            $this->assign_attribute($this->get_primary_key(), $value);
 
             return;
         }
 
-        foreach (static::$delegate as $item) {
+        foreach (static::$delegate as $key => $item) {
+            if ('processed' == $key) {
+                continue;
+            }
             if ($delegated_name = $this->is_delegated($name, $item)) {
                 $this->{$item['to']}->$delegated_name = $value;
 
@@ -628,7 +633,7 @@ public function &read_attribute(string $name)
         }
 
         if ('id' == $name) {
-            $pk = $this->get_primary_key(true);
+            $pk = $this->get_primary_key();
             if (isset($this->attributes[$pk])) {
                 return $this->attributes[$pk];
             }
@@ -659,7 +664,7 @@ public function &read_attribute(string $name)
     /**
      * @throws RelationshipException
      *
-     * @return Model|AbstractRelationship|null
+     * @return Model|array<Model>|null
      */
     protected function initRelationships(string $name): mixed
     {
@@ -717,14 +722,11 @@ public function attributes(): array
         return $this->attributes;
     }
 
-    /**
-     * @return array<string>|string
-     */
-    public function get_primary_key(bool $first = false): array|string
+    public function get_primary_key(): string
     {
         $pk = static::table()->pk;
 
-        return $first ? $pk[0] : $pk;
+        return $pk[0];
     }
 
     /**
@@ -805,14 +807,14 @@ public static function table_name()
      * @param string          $name     Name of an attribute
      * @param DelegateOptions $delegate An array containing delegate data
      */
-    private function is_delegated(string $name, $delegate): string|null
+    private function is_delegated(string $name, array $delegate): string|null
     {
         if (is_array($delegate)) {
-            if ('' != $delegate['prefix']) {
+            if (!empty($delegate['prefix'])) {
                 $name = substr($name, strlen($delegate['prefix']) + 1);
             }
 
-            if (in_array($name, $delegate['delegate'])) {
+            if (in_array($name, $delegate['delegate'] ?? [])) {
                 return $name;
             }
         }
@@ -951,7 +953,7 @@ private function insert($validate = true)
             $attributes = $this->attributes;
         }
 
-        $pk = $this->get_primary_key(true);
+        $pk = $this->get_primary_key();
         $use_sequence = false;
 
         if (!empty($table->sequence) && !isset($attributes[$pk])) {
@@ -1132,7 +1134,7 @@ public static function update_all(array $options = []): int
         $conn = static::connection();
         $sql = new SQLBuilder($conn, $table->get_fully_qualified_table_name());
 
-        $sql->update($options['set']);
+        isset($options['set']) && $sql->update($options['set']);
 
         if (isset($options['conditions']) && ($conditions = $options['conditions'])) {
             if (is_array($conditions) && !is_hash($conditions)) {
@@ -1399,7 +1401,7 @@ private function set_attributes_via_mass_assignment(array &$attributes, bool $gu
      *
      * @internal This should <strong>only</strong> be used by eager load
      */
-    public function set_relationship_from_eager_load(Model $model = null, string $name): void
+    public function set_relationship_from_eager_load(?Model $model, string $name): void
     {
         $table = static::table();
 
@@ -1411,8 +1413,9 @@ public function set_relationship_from_eager_load(Model $model = null, string $na
 
                     return;
                 }
-
-                $this->__relationships[$name][] = $model;
+                $this->__relationships[$name] ??= [];
+                assert(is_array($this->__relationships[$name]));
+                array_push($this->__relationships[$name], $model);
 
                 return;
             }
@@ -1435,9 +1438,9 @@ public function reload()
         $this->remove_from_cache();
 
         $this->__relationships = [];
-        $pk = array_values($this->get_values_for($this->get_primary_key()));
-
-        $this->set_attributes_via_mass_assignment($this->find($pk[0])->attributes, false);
+        $model = $this->find($this->{static::table()->pk[0]});
+        assert($model instanceof static);
+        $this->set_attributes_via_mass_assignment($model->attributes, false);
         $this->reset_dirty();
 
         return $this;
@@ -1597,11 +1600,12 @@ public function __call($method, $args)
      *
      * @see find
      *
-     * @return static[]
+     * @return array<int,static>
      */
-    public static function all(/* ... */)
+    public static function all(/* ... */): array
     {
-        return call_user_func_array(static::class . '::find', array_merge(['all'], func_get_args()));
+        /* @phpstan-ignore-next-line */
+        return static::find('all', ...func_get_args());
     }
 
     /**
@@ -1615,7 +1619,7 @@ public static function all(/* ... */)
      *
      * @return int Number of records that matched the query
      */
-    public static function count(/* ... */)
+    public static function count(/* ... */): int
     {
         $args = func_get_args();
         $options = static::extract_and_validate_options($args);
@@ -1625,7 +1629,7 @@ public static function count(/* ... */)
             if (is_hash($args[0])) {
                 $options['conditions'] = $args[0];
             } else {
-                $options['conditions'] = call_user_func_array(static::class . '::pk_conditions', $args);
+                $options['conditions'] = static::pk_conditions(...$args);
             }
         }
 
@@ -1643,41 +1647,43 @@ public static function count(/* ... */)
      *
      * ```
      * SomeModel::exists(123);
-     * SomeModel::exists(array('conditions' => array('id=? and name=?', 123, 'Tito')));
-     * SomeModel::exists(array('id' => 123, 'name' => 'Tito'));
+     * SomeModel::exists(['conditions' => ['id=? and name=?', 123, 'Tito']]);
+     * SomeModel::exists(['id' => 123, 'name' => 'Tito']);
      * ```
      *
      * @see find
-     *
-     * @return bool
      */
-    public static function exists(/* ... */)
+    public static function exists(/* ... */): bool
     {
-        return call_user_func_array(static::class . '::count', func_get_args()) > 0 ? true : false;
+        return static::count(...func_get_args()) > 0;
     }
 
     /**
      * Alias for self::find('first').
      *
      * @see find
-     *
-     * @return static|null The first matched record or null if not found
      */
-    public static function first(/* ... */)
+    public static function first(/* ... */): static|null
     {
-        return call_user_func_array(static::class . '::find', array_merge(['first'], func_get_args()));
+        $res = static::find('first', ...func_get_args());
+        // this is a workaround for what seems to be a PHPStan bug
+        assert($res instanceof static || is_null($res));
+
+        return $res;
     }
 
     /**
      * Alias for self::find('last')
      *
      * @see find
-     *
-     * @return Model|null The last matched record or null if not found
      */
-    public static function last(/* ... */)
+    public static function last(/* ... */): static|null
     {
-        return call_user_func_array(static::class . '::find', array_merge(['last'], func_get_args()));
+        $res = static::find('last', ...func_get_args());
+        // this is a workaround for what seems to be a PHPStan bug
+        assert($res instanceof static || is_null($res));
+
+        return $res;
     }
 
     /**
@@ -1803,7 +1809,7 @@ public static function find(/* $type, $options */): static|array|null
             $list = static::table()->find($options);
         }
 
-        return $single ? (!empty($list) ? $list[0] : null) : $list;
+        return $single ? ($list[0] ?? null) : $list;
     }
 
     /**
@@ -1855,6 +1861,7 @@ public static function find_by_pk(array|string|int|null $values, array $options,
             $pks = is_array($values) ? $values : [$values];
             $list = static::get_models_from_cache($pks);
         } else {
+            // int|string|array<int|string>
             $options['conditions'] = static::pk_conditions($values);
             $list = $table->find($options);
         }
@@ -1935,11 +1942,11 @@ public static function is_options_hash(mixed $options, bool $throw = true): bool
     /**
      * Returns a hash containing the names => values of the primary key.
      *
-     * @param int|array<number|string> $args Primary key value(s)
+     * @param PrimaryKey $args Primary key value(s)
      *
      * @return array<string, mixed>
      */
-    public static function pk_conditions(int|array $args): array
+    public static function pk_conditions(mixed $args): array
     {
         $table = static::table();
         $ret = [$table->pk[0] => $args];
@@ -2056,6 +2063,8 @@ private function serialize(string $type, array $options): string
         $class = 'ActiveRecord\\Serialize\\' . $type . 'Serializer';
         $serializer = new $class($this, $options);
 
+        assert($serializer instanceof Serialization);
+
         return $serializer->to_s();
     }
 
@@ -2069,7 +2078,7 @@ private function serialize(string $type, array $options): string
      *
      * @return bool True if invoked or null if not
      */
-    private function invoke_callback($method_name, $must_exist = true)
+    private function invoke_callback(string $method_name, bool $must_exist = true)
     {
         return static::table()->callback->invoke($this, $method_name, $must_exist);
     }
diff --git a/lib/PhpStan/FindDynamicMethodReturnTypeReflection.php b/lib/PhpStan/FindDynamicMethodReturnTypeReflection.php
index b4e3965f..6ff7f7f8 100644
--- a/lib/PhpStan/FindDynamicMethodReturnTypeReflection.php
+++ b/lib/PhpStan/FindDynamicMethodReturnTypeReflection.php
@@ -3,8 +3,9 @@
 namespace ActiveRecord\PhpStan;
 
 use ActiveRecord\Model;
-use PhpParser\Node\Expr;
+use PhpParser\Node\Arg;
 use PhpParser\Node\Expr\StaticCall;
+use PhpParser\Node\Name;
 use PHPStan\Analyser\Scope;
 use PHPStan\Reflection\MethodReflection;
 use PHPStan\Type\ArrayType;
@@ -32,12 +33,13 @@ public function isStaticMethodSupported(MethodReflection $methodReflection): boo
 
     public function getTypeFromStaticMethodCall(MethodReflection $methodReflection, StaticCall $methodCall, Scope $scope): Type
     {
-        $subclass = $methodCall->class . '';
+        assert($methodCall->class instanceof Name);
+        $subclass = $methodCall->class->toString();
         $args = $methodCall->args;
 
         $args = array_map(static function ($arg) use ($scope) {
+            assert($arg instanceof Arg);
             $val = $arg->value;
-            assert($val instanceof Expr);
 
             return $scope->getType($val);
         }, $args);
diff --git a/lib/Reflections.php b/lib/Reflections.php
index 6aedf58d..224073b6 100644
--- a/lib/Reflections.php
+++ b/lib/Reflections.php
@@ -29,11 +29,12 @@ class Reflections extends Singleton
      *
      * @return Reflections $this so you can chain calls like Reflections::instance()->add('class')->get()
      */
-    public function add(string $class = null): Reflections
+    public function add(string $class): Reflections
     {
         $class = $this->get_class($class);
 
         if (!isset($this->reflections[$class])) {
+            /* @phpstan-ignore-next-line */
             $this->reflections[$class] = new \ReflectionClass($class);
         }
 
@@ -57,19 +58,13 @@ public function destroy(string $class): void
     /**
      * Get a cached ReflectionClass.
      *
-     * @param class-string|object $className Optional name of a class or an instance of the class
+     * @param class-string $className Optional name of a class or an instance of the class
      *
      * @throws ActiveRecordException if class was not found
-     *
-     * @return mixed null or a ReflectionClass instance
      */
-    public function get($className)
+    public function get(string $className): \ReflectionClass
     {
-        if (isset($this->reflections[$className])) {
-            return $this->reflections[$className];
-        }
-
-        throw new ActiveRecordException("Class not found: $className");
+        return $this->reflections[$className] ?? throw new ActiveRecordException("Class not found: $className");
     }
 
     /**
@@ -77,7 +72,7 @@ public function get($className)
      *
      * @param class-string|object $class An object or name of a class
      *
-     * @return string
+     * @return class-string
      */
     private function get_class(string|object $class = null)
     {
@@ -85,10 +80,6 @@ private function get_class(string|object $class = null)
             return get_class($class);
         }
 
-        if (!is_null($class)) {
-            return $class;
-        }
-
-        return $this->get_called_class();
+        return $class;
     }
 }
diff --git a/lib/Relationship/AbstractRelationship.php b/lib/Relationship/AbstractRelationship.php
index 3eddbfdf..fcc4eaef 100644
--- a/lib/Relationship/AbstractRelationship.php
+++ b/lib/Relationship/AbstractRelationship.php
@@ -4,7 +4,6 @@
 
 use function ActiveRecord\all;
 use function ActiveRecord\classify;
-use function ActiveRecord\denamespace;
 
 use ActiveRecord\Exception\RelationshipException;
 
@@ -36,16 +35,16 @@ abstract class AbstractRelationship
     /**
      * Class name of the associated model.
      *
-     * @var string
+     * @var class-string
      */
     public $class_name;
 
     /**
      * Name of the foreign key.
      *
-     * @var string|string[]
+     * @var string[]
      */
-    public mixed $foreign_key = [];
+    public array $foreign_key = [];
 
     /**
      * Options of the relationship.
@@ -54,45 +53,39 @@ abstract class AbstractRelationship
      */
     protected array $options = [];
 
-    /**
-     * Is the relationship single or multi.
-     */
-    protected bool $poly_relationship = false;
-
     /**
      * List of valid options for relationships.
      *
      * @var array<string>
      */
-    protected static $valid_association_options = ['class_name', 'class', 'foreign_key', 'conditions', 'select', 'readonly', 'namespace'];
+    protected static $valid_association_options = [
+        'class_name',
+        'foreign_key',
+        'conditions',
+        'select',
+        'readonly',
+        'namespace'
+    ];
 
     /**
      * Constructs a relationship.
      *
      * @param array<mixed> $options Options for the relationship (see {@link valid_association_options})
      */
-    public function __construct(string $attribute_name, $options = [])
+    public function __construct(string $attribute_name, array $options = [])
     {
         $this->attribute_name = $attribute_name;
         $this->options = $this->merge_association_options($options);
 
-        $relationship = strtolower(denamespace(get_called_class()));
-
-        if ('hasmany' === $relationship || 'hasandbelongstomany' === $relationship) {
-            $this->poly_relationship = true;
-        }
-
         if (isset($this->options['conditions']) && !is_array($this->options['conditions'])) {
             $this->options['conditions'] = [$this->options['conditions']];
         }
 
-        if (isset($this->options['class'])) {
-            $this->set_class_name($this->options['class']);
-        } elseif (isset($this->options['class_name'])) {
-            $this->set_class_name($this->options['class_name']);
+        if (isset($this->options['class_name'])) {
+            $this->set_class_name($this->inferred_class_name($this->options['class_name']));
         }
 
-        $this->attribute_name = strtolower(Inflector::instance()->variablize($this->attribute_name));
+        $this->attribute_name = strtolower(Inflector::variablize($this->attribute_name));
 
         if (!$this->foreign_key && isset($this->options['foreign_key'])) {
             $this->foreign_key = is_array($this->options['foreign_key']) ? $this->options['foreign_key'] : [$this->options['foreign_key']];
@@ -116,7 +109,7 @@ abstract public function load_eagerly(array $models, array $attributes, array $i
      */
     public function is_poly(): bool
     {
-        return $this->poly_relationship;
+        return false;
     }
 
     /**
@@ -136,12 +129,11 @@ protected function query_and_attach_related_models_eagerly(Table $table, array $
     {
         $values = [];
         $options = $this->options;
-        $inflector = Inflector::instance();
         $query_key = $query_keys[0];
         $model_values_key = $model_values_keys[0];
 
         foreach ($attributes as $column => $value) {
-            $values[] = $value[$inflector->variablize($model_values_key)];
+            $values[] = $value[Inflector::variablize($model_values_key)];
         }
 
         $values = [$values];
@@ -192,8 +184,8 @@ protected function query_and_attach_related_models_eagerly(Table $table, array $
         $related_models = $class::find('all', $options);
         $used_models_map = [];
         $related_models_map = [];
-        $model_values_key = $inflector->variablize($model_values_key);
-        $query_key = $inflector->variablize($query_key);
+        $model_values_key = Inflector::variablize($model_values_key);
+        $query_key = Inflector::variablize($query_key);
 
         foreach ($related_models as $related) {
             $related_models_map[$related->$query_key][] = $related;
@@ -231,7 +223,10 @@ public function build_association(Model $model, array $attributes = [], bool $gu
     {
         $class_name = $this->class_name;
 
-        return new $class_name($attributes, $guard_attributes);
+        $model = new $class_name($attributes, $guard_attributes);
+        assert($model instanceof Model);
+
+        return $model;
     }
 
     /**
@@ -253,7 +248,7 @@ protected function append_record_to_associate(Model $associate, Model $record):
     {
         $association = &$associate->{$this->attribute_name};
 
-        if ($this->poly_relationship) {
+        if ($this->is_poly()) {
             $association[] = $record;
         } else {
             $association = $record;
@@ -296,24 +291,32 @@ protected function unset_non_finder_options(array $options): array
     }
 
     /**
-     * Infers the $this->class_name based on $this->attribute_name.
-     *
-     * Will try to guess the appropriate class by singularizing and uppercasing $this->attribute_name.
-     *
-     * @see attribute_name
+     * @return class-string
      */
-    protected function set_inferred_class_name(): void
+    protected function inferred_class_name(string $name): string
     {
-        $singularize = ($this instanceof HasMany ? true : false);
-        $this->set_class_name(classify($this->attribute_name, $singularize));
+        if (!has_absolute_namespace($name) && isset($this->options['namespace'])) {
+            if (!isset($this->options['class_name'])) {
+                $name = classify($name, $this instanceof HasMany);
+            }
+            $name = $this->options['namespace'] . '\\' . $name;
+        }
+
+        if (!class_exists($name)) {
+            throw new \ReflectionException('Unknown class name: ' . $name);
+        }
+
+        return $name;
     }
 
+    /**
+     * @param class-string $class_name
+     *
+     * @throws RelationshipException
+     * @throws \ActiveRecord\Exception\ActiveRecordException
+     */
     protected function set_class_name(string $class_name): void
     {
-        if (!has_absolute_namespace($class_name) && isset($this->options['namespace'])) {
-            $class_name = $this->options['namespace'] . '\\' . $class_name;
-        }
-
         $reflection = Reflections::instance()->add($class_name)->get($class_name);
 
         if (!$reflection->isSubClassOf('ActiveRecord\\Model')) {
diff --git a/lib/Relationship/BelongsTo.php b/lib/Relationship/BelongsTo.php
index 3a2af949..297dfd36 100644
--- a/lib/Relationship/BelongsTo.php
+++ b/lib/Relationship/BelongsTo.php
@@ -41,6 +41,9 @@
  */
 class BelongsTo extends AbstractRelationship
 {
+    /**
+     * @var class-string
+     */
     public $class_name;
 
     /**
@@ -63,22 +66,22 @@ public function __construct(string $attributeName, $options = [])
         parent::__construct($attributeName, $options);
 
         if (!$this->class_name) {
-            $this->set_inferred_class_name();
+            $this->set_class_name(
+                $this->inferred_class_name($this->attribute_name)
+            );
         }
 
         // infer from class_name
         if (!$this->foreign_key) {
-            $this->foreign_key = [Inflector::instance()->keyify($this->class_name)];
+            $this->foreign_key = [Inflector::keyify($this->class_name)];
         }
     }
 
     public function load(Model $model): ?Model
     {
         $keys = [];
-        $inflector = Inflector::instance();
-
         foreach ($this->foreign_key as $key) {
-            $keys[] = $inflector->variablize($key);
+            $keys[] = Inflector::variablize($key);
         }
 
         if (!($conditions = $this->create_conditions_from_keys($model, $this->primary_key(), $keys))) {
diff --git a/lib/Relationship/HasAndBelongsToMany.php b/lib/Relationship/HasAndBelongsToMany.php
index 44811975..67b495eb 100644
--- a/lib/Relationship/HasAndBelongsToMany.php
+++ b/lib/Relationship/HasAndBelongsToMany.php
@@ -26,6 +26,11 @@ public function __construct($options = [])
         parent::__construct($options[0], $options);
     }
 
+    public function is_poly(): bool
+    {
+        return true;
+    }
+
     public function load(Model $model): mixed
     {
         throw new \Exception("HasAndBelongsToMany doesn't need to load anything.");
diff --git a/lib/Relationship/HasMany.php b/lib/Relationship/HasMany.php
index 4b1d1d00..7821bad2 100644
--- a/lib/Relationship/HasMany.php
+++ b/lib/Relationship/HasMany.php
@@ -72,12 +72,17 @@ class HasMany extends AbstractRelationship
     ];
 
     /**
-     * @var string|array<string>
+     * @var array<string>
      */
-    protected string|array $primary_key;
+    protected array $primary_key;
 
     private string $through;
 
+    public function is_poly(): bool
+    {
+        return true;
+    }
+
     /**
      * Constructs a {@link HasMany} relationship.
      *
@@ -91,7 +96,7 @@ public function __construct(string $attribute, array $options = [])
             $this->through = $this->options['through'];
 
             if (isset($this->options['source'])) {
-                $this->set_class_name($this->options['source']);
+                $this->set_class_name($this->inferred_class_name($this->options['source']));
             }
         }
 
@@ -100,15 +105,18 @@ public function __construct(string $attribute, array $options = [])
         }
 
         if (!$this->class_name) {
-            $this->set_inferred_class_name();
+            $this->set_class_name($this->inferred_class_name($this->attribute_name));
         }
     }
 
+    /**
+     * @param class-string $model_class_name
+     */
     protected function set_keys(string $model_class_name, bool $override = false): void
     {
         // infer from class_name
         if (!$this->foreign_key || $override) {
-            $this->foreign_key = [Inflector::instance()->keyify($model_class_name)];
+            $this->foreign_key = [Inflector::keyify($model_class_name)];
         }
 
         if (!isset($this->primary_key) || $override) {
@@ -165,7 +173,7 @@ public function load(Model $model): mixed
         $options = $this->unset_non_finder_options($this->options);
         $options['conditions'] = $conditions;
 
-        $res = $class_name::find($this->poly_relationship ? 'all' : 'first', $options);
+        $res = $class_name::find($this->is_poly() ? 'all' : 'first', $options);
 
         return $res;
     }
@@ -178,7 +186,7 @@ public function load(Model $model): mixed
     private function get_foreign_key_for_new_association(Model $model): array
     {
         $this->set_keys(get_class($model));
-        $primary_key = Inflector::instance()->variablize($this->foreign_key[0]);
+        $primary_key = Inflector::variablize($this->foreign_key[0]);
 
         /*
          * TODO: set up model property reflection stanning
diff --git a/lib/Relationship/HasOne.php b/lib/Relationship/HasOne.php
index 15698202..9f9cdbd2 100644
--- a/lib/Relationship/HasOne.php
+++ b/lib/Relationship/HasOne.php
@@ -23,4 +23,8 @@
  */
 class HasOne extends HasMany
 {
+    public function is_poly(): bool
+    {
+        return false;
+    }
 }
diff --git a/lib/SQLBuilder.php b/lib/SQLBuilder.php
index be5b58fb..23b57809 100644
--- a/lib/SQLBuilder.php
+++ b/lib/SQLBuilder.php
@@ -115,7 +115,33 @@ public function get_where_values(): array
 
     public function where(/* (conditions, values) || (hash) */): static
     {
-        $this->apply_where_conditions(func_get_args());
+        $args = func_get_args();
+        $num_args = count($args);
+
+        if (1 == $num_args && is_hash($args[0])) {
+            $hash = empty($this->joins) ? $args[0] : $this->prepend_table_name_to_fields($args[0]);
+            $e = new Expressions($this->connection, $hash);
+            $this->where = $e->to_s();
+            $this->where_values = array_flatten($e->values());
+        } elseif ($num_args > 0) {
+            // if the values has a nested array then we'll need to use Expressions to expand the bind marker for us
+            $values = array_slice($args, 1);
+
+            foreach ($values as $name => &$value) {
+                if (is_array($value)) {
+                    $e = new Expressions($this->connection, $args[0]);
+                    $e->bind_values($values);
+                    $this->where = $e->to_s();
+                    $this->where_values = array_flatten($e->values());
+
+                    return $this;
+                }
+            }
+
+            // no nested array so nothing special to do
+            $this->where = $args[0] ?? '';
+            $this->where_values = $values;
+        }
 
         return $this;
     }
@@ -163,12 +189,7 @@ public function select(string $select): static
         return $this;
     }
 
-    /**
-     * @param string|array<string> $joins
-     *
-     * @return $this
-     */
-    public function joins(string|array $joins): static
+    public function joins(string $joins): static
     {
         $this->joins = $joins;
 
@@ -220,7 +241,7 @@ public function update(array|string $mixed): static
     public function delete(): static
     {
         $this->operation = 'DELETE';
-        $this->apply_where_conditions(func_get_args());
+        $this->where(...func_get_args());
 
         return $this;
     }
@@ -256,7 +277,10 @@ public static function reverse_order(string $order = ''): string
      */
     public static function underscored_string_to_parts(string $string, int $flags=PREG_SPLIT_DELIM_CAPTURE): array
     {
-        return preg_split('/(_and_|_or_)/i', $string, -1, $flags);
+        $res = preg_split('/(_and_|_or_)/i', $string, -1, $flags);
+        assert(is_array($res));
+
+        return $res;
     }
 
     /**
@@ -353,41 +377,6 @@ private function prepend_table_name_to_fields(array $hash = [])
         return $new;
     }
 
-    /**
-     * @param array<string|array<string,mixed>> $args
-     *
-     * @throws Exception\ExpressionsException
-     */
-    private function apply_where_conditions(array $args): void
-    {
-        $num_args = count($args);
-
-        if (1 == $num_args && is_hash($args[0])) {
-            $hash = empty($this->joins) ? $args[0] : $this->prepend_table_name_to_fields($args[0]);
-            $e = new Expressions($this->connection, $hash);
-            $this->where = $e->to_s();
-            $this->where_values = array_flatten($e->values());
-        } elseif ($num_args > 0) {
-            // if the values has a nested array then we'll need to use Expressions to expand the bind marker for us
-            $values = array_slice($args, 1);
-
-            foreach ($values as $name => &$value) {
-                if (is_array($value)) {
-                    $e = new Expressions($this->connection, $args[0]);
-                    $e->bind_values($values);
-                    $this->where = $e->to_s();
-                    $this->where_values = array_flatten($e->values());
-
-                    return;
-                }
-            }
-
-            // no nested array so nothing special to do
-            $this->where = $args[0] ?? '';
-            $this->where_values = &$values;
-        }
-    }
-
     private function build_delete(): string
     {
         $sql = "DELETE FROM $this->table";
diff --git a/lib/Serialize/CsvSerializer.php b/lib/Serialize/CsvSerializer.php
index f7e46169..4c55c32e 100644
--- a/lib/Serialize/CsvSerializer.php
+++ b/lib/Serialize/CsvSerializer.php
@@ -12,7 +12,7 @@ class CsvSerializer extends Serialization
 
     public function to_s(): string
     {
-        if (true == @$this->options['only_header']) {
+        if ($this->options['only_header'] ?? false) {
             return $this->header();
         }
 
@@ -35,9 +35,12 @@ private function row(): string
     private function to_csv(array $arr): string
     {
         $outstream = fopen('php://temp', 'w');
+        assert(false !== $outstream);
         fputcsv($outstream, $arr, self::$delimiter, self::$enclosure);
         rewind($outstream);
-        $buffer = trim(stream_get_contents($outstream));
+        $contents = stream_get_contents($outstream);
+        assert(is_string($contents));
+        $buffer = trim($contents);
         fclose($outstream);
 
         return $buffer;
diff --git a/lib/Serialize/JsonSerializer.php b/lib/Serialize/JsonSerializer.php
index 6e9ce560..266bb2c4 100644
--- a/lib/Serialize/JsonSerializer.php
+++ b/lib/Serialize/JsonSerializer.php
@@ -2,6 +2,8 @@
 
 namespace ActiveRecord\Serialize;
 
+use ActiveRecord\Model;
+
 /**
  * JSON serializer.
  *
@@ -9,10 +11,16 @@
  */
 class JsonSerializer extends Serialization
 {
+    public function __construct(Model $model, $options)
+    {
+        parent::__construct($model, $options);
+    }
+
     public function to_s(): string
     {
-        $res = !empty($this->options['include_root']) ? [strtolower(get_class($this->model)) => $this->to_a()] : $this->to_a();
+        $res = json_encode(!empty($this->options['include_root']) ? [strtolower(get_class($this->model)) => $this->to_a()] : $this->to_a());
+        assert(is_string($res));
 
-        return json_encode($res);
+        return $res;
     }
 }
diff --git a/lib/Serialize/Serialization.php b/lib/Serialize/Serialization.php
index 07666401..1d6f5c2c 100644
--- a/lib/Serialize/Serialization.php
+++ b/lib/Serialize/Serialization.php
@@ -2,7 +2,7 @@
 
 namespace ActiveRecord\Serialize;
 
-use ActiveRecord\Config;
+use ActiveRecord\DateTimeInterface;
 use ActiveRecord\Exception\UndefinedPropertyException;
 use ActiveRecord\Model;
 use ActiveRecord\Types;
@@ -123,9 +123,10 @@ private function parse_options(): void
     private function check_only(): void
     {
         if (isset($this->options['only'])) {
-            $this->options_to_a('only');
-
-            $exclude = array_diff(array_keys($this->attributes), $this->options['only']);
+            $exclude = array_diff(
+                array_keys($this->attributes),
+                $this->value_to_a($this->options['only'])
+            );
             $this->attributes = array_diff_key($this->attributes, array_flip($exclude));
         }
     }
@@ -133,18 +134,23 @@ private function check_only(): void
     private function check_except(): void
     {
         if (isset($this->options['except']) && !isset($this->options['only'])) {
-            $this->options_to_a('except');
-            $this->attributes = array_diff_key($this->attributes, array_flip($this->options['except']));
+            $this->attributes = array_diff_key(
+                $this->attributes,
+                array_flip($this->value_to_a($this->options['except']))
+            );
         }
     }
 
     private function check_methods(): void
     {
         if (isset($this->options['methods'])) {
-            $this->options_to_a('methods');
-
-            foreach ($this->options['methods'] as $method) {
+            foreach ($this->value_to_a($this->options['methods']) as $method) {
                 if (method_exists($this->model, $method)) {
+                    /*
+                     * PHPStan complains about this, and I don't know why. Skipping, for now.
+                     *
+                     * @phpstan-ignore-next-line
+                     */
                     $this->attributes[$method] = $this->model->$method();
                 }
             }
@@ -164,21 +170,20 @@ private function check_only_method(): void
     private function check_include(): void
     {
         if (isset($this->options['include'])) {
-            $this->options_to_a('include');
-
             $serializer_class = get_class($this);
 
-            foreach ($this->options['include'] as $association => $options) {
+            foreach ($this->value_to_a($this->options['include']) as $association => $options) {
                 if (!is_array($options)) {
                     $association = $options;
                     $options = [];
                 }
+                assert(is_string($association));
 
                 try {
                     $assoc = $this->model->$association;
 
                     if (null === $assoc) {
-                        $this->attributes[$association] = null;
+                        unset($this->attributes[$association]);
                     } elseif (!is_array($assoc)) {
                         $serialized = new $serializer_class($assoc, $options);
                         $this->attributes[$association] = $serialized->to_a();
@@ -189,7 +194,9 @@ private function check_include(): void
                             $serialized = new $serializer_class($a, $options);
 
                             if ($this->includes_with_class_name_element) {
-                                $includes[strtolower(get_class($a))][] = $serialized->to_a();
+                                $className = get_class($a);
+                                assert(is_string($className));
+                                $includes[strtolower($className)][] = $serialized->to_a();
                             } else {
                                 $includes[] = $serialized->to_a();
                             }
@@ -204,11 +211,16 @@ private function check_include(): void
         }
     }
 
-    final protected function options_to_a(string $key): void
+    /**
+     * @return array<mixed>
+     */
+    final protected function value_to_a(mixed $value): array
     {
-        if (!is_array($this->options[$key])) {
-            $this->options[$key] = [$this->options[$key]];
+        if (!is_array($value)) {
+            return [$value];
         }
+
+        return $value;
     }
 
     /**
@@ -218,9 +230,8 @@ final protected function options_to_a(string $key): void
      */
     final public function to_a(): array
     {
-        $date_class = Config::instance()->get_date_class();
         foreach ($this->attributes as &$value) {
-            if ($value instanceof $date_class) {
+            if ($value instanceof DateTimeInterface) {
                 $value = $value->format(self::$DATETIME_FORMAT);
             }
         }
diff --git a/lib/Serialize/XmlSerializer.php b/lib/Serialize/XmlSerializer.php
index 6cd5ac34..e9b556c8 100644
--- a/lib/Serialize/XmlSerializer.php
+++ b/lib/Serialize/XmlSerializer.php
@@ -43,9 +43,9 @@ private function xml_encode(): string
         $this->write($this->to_a());
         $this->writer->endElement();
         $this->writer->endDocument();
-        $xml = $this->writer->outputMemory(true);
+        $xml = $this->writer->outputMemory();
 
-        if (true == @$this->options['skip_instruct']) {
+        if ($this->options['skip_instruct'] ?? false) {
             $xml = preg_replace('/<\?xml version.*?\?>/', '', $xml);
         }
 
@@ -59,8 +59,7 @@ private function write(array $data, string $tag = null): void
     {
         foreach ($data as $attr => $value) {
             $attr = $tag ?? $attr;
-
-            if (is_array($value) || is_object($value)) {
+            if (is_array($value)) {
                 if (!is_int(key($value))) {
                     $this->writer->startElement(denamespace($attr));
                     $this->write($value);
diff --git a/lib/Singleton.php b/lib/Singleton.php
index a838a3bd..fe9ee5c0 100644
--- a/lib/Singleton.php
+++ b/lib/Singleton.php
@@ -44,16 +44,4 @@ final public static function instance(): static
     private function __clone()
     {
     }
-
-    /**
-     * Similar to a get_called_class() for a child class to invoke.
-     *
-     * @return string
-     */
-    final protected function get_called_class()
-    {
-        $backtrace = debug_backtrace();
-
-        return get_class($backtrace[2]['object']);
-    }
 }
diff --git a/lib/Table.php b/lib/Table.php
index 895f8a9d..310873a0 100644
--- a/lib/Table.php
+++ b/lib/Table.php
@@ -20,12 +20,12 @@
  * reading and writing to its database table. There is one instance of Table
  * for every table you have a model for.
  *
- * @package ActiveRecord
+ * @phpstan-import-type PrimaryKey from Types
  */
 class Table
 {
     /**
-     * @var array<string, Model>
+     * @var array<string, Table>
      */
     private static array $cache = [];
 
@@ -73,18 +73,17 @@ class Table
 
     /**
      * A instance of CallBack for this model/table
-     *
-     * @static
-     *
-     * @var object ActiveRecord\CallBack
      */
-    public $callback;
+    public CallBack $callback;
 
     /**
      * @var array<string, AbstractRelationship>
      */
     private array $relationships = [];
 
+    /**
+     * @param class-string $model_class_name
+     */
     public static function load(string $model_class_name): Table
     {
         if (!isset(self::$cache[$model_class_name])) {
@@ -106,6 +105,11 @@ public static function clear_cache(string $model_class_name = null): void
         }
     }
 
+    /**
+     * @param class-string $class_name
+     *
+     * @throws Exception\ActiveRecordException
+     */
     public function __construct(string $class_name)
     {
         $this->class = Reflections::instance()->add($class_name)->get($class_name);
@@ -262,9 +266,9 @@ public function find(array $options): array
     }
 
     /**
-     * @param string|array<string> $pk
+     * @param PrimaryKey $pk
      */
-    public function cache_key_for_model(string|array $pk): string
+    public function cache_key_for_model(mixed $pk): string
     {
         if (is_array($pk)) {
             $pk = implode('-', $pk);
@@ -499,13 +503,13 @@ private function map_names(array &$hash, array &$map): array
     private function process_data(array|null $hash): array|null
     {
         if ($hash) {
-            $date_class = Config::instance()->get_date_class();
             foreach ($hash as $name => $value) {
-                if ($value instanceof $date_class || $value instanceof \DateTime) {
-                    if (isset($this->columns[$name]) && Column::DATE == $this->columns[$name]->type) {
-                        $hash[$name] = $this->conn->date_to_string($value);
+                if ($value instanceof \DateTime) {
+                    $column = $this->columns[$name] ?? null;
+                    if (isset($column) && Column::DATE == $column->type) {
+                        $hash[$name] = $this->conn->date_string($value);
                     } else {
-                        $hash[$name] = $this->conn->datetime_to_string($value);
+                        $hash[$name] = $this->conn->datetime_string($value);
                     }
                 } else {
                     $hash[$name] = $value;
@@ -537,7 +541,7 @@ private function set_table_name(): void
             $this->table = $table;
         } else {
             // infer table name from the class name
-            $this->table = Inflector::instance()->tableize($this->class->getName());
+            $this->table = Inflector::tableize($this->class->getName());
 
             // strip namespaces from the table name if any
             $parts = explode('\\', $this->table);
@@ -557,7 +561,8 @@ private function set_cache(): void
 
         $model_class_name = $this->class->name;
         $this->cache_individual_model = $model_class_name::$cache;
-        $this->cache_model_expire = $model_class_name::$cache_expire ?? Cache::$options['expire'];
+
+        $this->cache_model_expire = $model_class_name::$cache_expire ?? Cache::$options['expire'] ?? 0;
     }
 
     private function set_sequence_name(): void
diff --git a/lib/Utils.php b/lib/Utils.php
index d7a58ed0..5718f3ee 100644
--- a/lib/Utils.php
+++ b/lib/Utils.php
@@ -34,15 +34,17 @@
 
 namespace ActiveRecord;
 
-function classify(string $class_name, bool $singular = false): string
+function classify(string $string, bool $singular = false): string
 {
     if ($singular) {
-        $class_name = Utils::singularize($class_name);
+        $string = Utils::singularize($string);
     }
 
-    $class_name = Inflector::instance()->camelize($class_name);
+    $string = Inflector::camelize($string);
 
-    return ucfirst($class_name);
+    $res = ucfirst($string);
+
+    return $res;
 }
 
 /**
@@ -196,9 +198,8 @@ public static function add_condition(array &$conditions, string|array $condition
 
     public static function human_attribute(string $attr): string
     {
-        $inflector = Inflector::instance();
-        $inflected = $inflector->variablize($attr);
-        $normal = $inflector->uncamelize($inflected);
+        $inflected = Inflector::variablize($attr);
+        $normal = Inflector::uncamelize($inflected);
 
         return ucfirst(str_replace('_', ' ', $normal));
     }
@@ -366,11 +367,11 @@ public static function singularize(string $string): string
         return $string;
     }
 
-    /**
-     * @return string|string[]|null
-     */
-    public static function squeeze(string $char, string $string): mixed
+    public static function squeeze(string $char, string $string): string
     {
-        return preg_replace("/$char+/", $char, $string);
+        $res = preg_replace("/$char+/", $char, $string);
+        assert(is_string($res));
+
+        return $res;
     }
 }
diff --git a/lib/Validations.php b/lib/Validations.php
index f428a363..049efe35 100644
--- a/lib/Validations.php
+++ b/lib/Validations.php
@@ -115,16 +115,6 @@ class Validations
         'validates_uniqueness_of'
     ];
 
-    /**
-     * @var ValidationOptions
-     */
-    private static array $DEFAULT_VALIDATION_OPTIONS = [
-        'on' => 'save',
-        'allow_null' => false,
-        'allow_blank' => false,
-        'message' => null,
-    ];
-
     /**
      * @var array<string>
      */
@@ -148,7 +138,12 @@ public function __construct(Model $model)
         $this->model = $model;
         $this->errors = new ValidationErrors($this->model);
         $this->klass = Reflections::instance()->get(get_class($this->model));
-        $this->validators = array_intersect(array_keys($this->klass->getStaticProperties()), self::$VALIDATION_FUNCTIONS);
+        /** @var array<string,string> $validators */
+        $validators = array_intersect(
+            array_keys($this->klass->getStaticProperties()),
+            self::$VALIDATION_FUNCTIONS
+        );
+        $this->validators = $validators;
     }
 
     public function get_errors(): ValidationErrors
@@ -314,9 +309,7 @@ public function validates_inclusion_or_exclusion_of(string $type, array $attrs):
         foreach ($attrs as $attribute => $options) {
             $var = $this->model->$attribute;
 
-            $enum = $options['in'] ?? $options['within'];
-            assert(isset($enum));
-
+            $enum = $options['in'] ?? $options['within'] ?? throw new \Exception("Must provide 'in' or 'within'");
             $message = str_replace('%s', $var ?? '', $options['message'] ?? ValidationErrors::$DEFAULT_ERROR_MESSAGES[$type]);
 
             if ($this->is_null_with_option($var, $options) || $this->is_blank_with_option($var, $options)) {
@@ -559,13 +552,13 @@ public function validates_uniqueness_of($attrs): void
                 $options = [];
             }
             $pk = $this->model->get_primary_key();
-            $pk_value = $this->model->{$pk[0]};
+            $pk_value = $this->model->{$pk};
 
             $fields = array_merge([$attr], $options['scope'] ?? []);
             $add_record = join('_and_', $fields);
 
             $conditions = [''];
-            $pk_quoted = $connection->quote_name($pk[0]);
+            $pk_quoted = $connection->quote_name($pk);
             if (null === $pk_value) {
                 $sql = "{$pk_quoted} IS NOT NULL";
             } else {
@@ -593,7 +586,7 @@ public function validates_uniqueness_of($attrs): void
      */
     private function is_null_with_option(mixed $var, array &$options): bool
     {
-        return is_null($var) && ($options['allow_null'] ?? self::$DEFAULT_VALIDATION_OPTIONS['allow_null']);
+        return is_null($var) && ($options['allow_null'] ?? false);
     }
 
     /**
@@ -601,6 +594,6 @@ private function is_null_with_option(mixed $var, array &$options): bool
      */
     private function is_blank_with_option(mixed $var, array &$options): bool
     {
-        return Utils::is_blank($var) && ($options['allow_blank'] ?? self::$DEFAULT_VALIDATION_OPTIONS['allow_blank']);
+        return Utils::is_blank($var) && ($options['allow_blank'] ?? false);
     }
 }
diff --git a/lib/cache/Memcache.php b/lib/cache/Memcache.php
index 2fe8a0a8..ee4cfbb6 100644
--- a/lib/cache/Memcache.php
+++ b/lib/cache/Memcache.php
@@ -6,8 +6,8 @@
 
 /**
  * @phpstan-type MemcacheOptions array{
- *      host?: string,
- *      port?: string
+ *      host: string,
+ *      port?: int
  *  }
  */
 class Memcache
@@ -24,13 +24,12 @@ class Memcache
     public function __construct(array $options)
     {
         $this->memcache = new \Memcache();
-        $options['port'] = $options['port'] ?? self::DEFAULT_PORT;
-
-        if (!@$this->memcache->connect($options['host'], $options['port'])) {
+        $port = $options['port'] ?? self::DEFAULT_PORT;
+        if (!@$this->memcache->connect($options['host'], $port)) {
             if ($error = error_get_last()) {
                 $message = $error['message'];
             } else {
-                $message = sprintf('Could not connect to %s:%s', $options['host'], $options['port']);
+                $message = sprintf('Could not connect to %s:%s', $options['host'], $port);
             }
             throw new CacheException($message);
         }
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 5dca0cd0..f421b5f0 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -1,11 +1,12 @@
 parameters:
-    level: 6
+    level: 7
     tmpDir: .stan-cache
     paths:
         - %currentWorkingDirectory%/lib
         - %currentWorkingDirectory%/test/phpstan
 
     reportUnmatchedIgnoredErrors: false
+    checkGenericClassInNonGenericObjectType: false
     ignoreErrors:
 
 services:
diff --git a/test/ActiveRecordFindTest.php b/test/ActiveRecordFindTest.php
index a0859875..dd93f9b3 100644
--- a/test/ActiveRecordFindTest.php
+++ b/test/ActiveRecordFindTest.php
@@ -418,7 +418,7 @@ public function testFindWithSelectNonSelectedFieldsShouldNotHaveAttributes()
     public function testJoinsOnModelWithAssociationAndExplicitJoins()
     {
         JoinBook::$belongs_to = [
-            'author' => true
+            'author'=>true
         ];
         JoinBook::first(['joins' => ['author', 'LEFT JOIN authors a ON(books.secondary_author_id=a.author_id)']]);
         $this->assert_sql_has('INNER JOIN authors ON(books.author_id = authors.author_id)', JoinBook::table()->last_sql);
diff --git a/test/ConnectionTest.php b/test/ConnectionTest.php
index 159202bc..a8b633e0 100644
--- a/test/ConnectionTest.php
+++ b/test/ConnectionTest.php
@@ -18,18 +18,18 @@ public function testConnectionInfoFromShouldThrowExceptionWhenNoHost()
     public function testConnectionInfo()
     {
         $info = ActiveRecord\Connection::parse_connection_url('mysql://user:pass@127.0.0.1:3306/dbname');
-        $this->assertEquals('mysql', $info->protocol);
-        $this->assertEquals('user', $info->user);
-        $this->assertEquals('pass', $info->pass);
-        $this->assertEquals('127.0.0.1', $info->host);
-        $this->assertEquals(3306, $info->port);
-        $this->assertEquals('dbname', $info->db);
+        $this->assertEquals('mysql', $info['protocol']);
+        $this->assertEquals('user', $info['user']);
+        $this->assertEquals('pass', $info['pass']);
+        $this->assertEquals('127.0.0.1', $info['host']);
+        $this->assertEquals(3306, $info['port']);
+        $this->assertEquals('dbname', $info['db']);
     }
 
     public function testGh103SqliteConnectionStringRelative()
     {
         $info = ActiveRecord\Connection::parse_connection_url('sqlite://../some/path/to/file.db');
-        $this->assertEquals('../some/path/to/file.db', $info->host);
+        $this->assertEquals('../some/path/to/file.db', $info['host']);
     }
 
     public function testGh103SqliteConnectionStringAbsolute()
@@ -41,37 +41,37 @@ public function testGh103SqliteConnectionStringAbsolute()
     public function testGh103SqliteConnectionStringUnix()
     {
         $info = ActiveRecord\Connection::parse_connection_url('sqlite://unix(/some/path/to/file.db)');
-        $this->assertEquals('/some/path/to/file.db', $info->host);
+        $this->assertEquals('/some/path/to/file.db', $info['host']);
 
         $info = ActiveRecord\Connection::parse_connection_url('sqlite://unix(/some/path/to/file.db)/');
-        $this->assertEquals('/some/path/to/file.db', $info->host);
+        $this->assertEquals('/some/path/to/file.db', $info['host']);
 
         $info = ActiveRecord\Connection::parse_connection_url('sqlite://unix(/some/path/to/file.db)/dummy');
-        $this->assertEquals('/some/path/to/file.db', $info->host);
+        $this->assertEquals('/some/path/to/file.db', $info['host']);
     }
 
     public function testGh103SqliteConnectionStringWindows()
     {
         $info = ActiveRecord\Connection::parse_connection_url('sqlite://windows(c%3A/some/path/to/file.db)');
-        $this->assertEquals('c:/some/path/to/file.db', $info->host);
+        $this->assertEquals('c:/some/path/to/file.db', $info['host']);
     }
 
     public function testParseConnectionUrlWithUnixSockets()
     {
         $info = ActiveRecord\Connection::parse_connection_url('mysql://user:password@unix(/tmp/mysql.sock)/database');
-        $this->assertEquals('/tmp/mysql.sock', $info->host);
+        $this->assertEquals('/tmp/mysql.sock', $info['host']);
     }
 
     public function testParseConnectionUrlWithDecodeOption()
     {
         $info = ActiveRecord\Connection::parse_connection_url('mysql://h%20az:h%40i@127.0.0.1/test?decode=true');
-        $this->assertEquals('h az', $info->user);
-        $this->assertEquals('h@i', $info->pass);
+        $this->assertEquals('h az', $info['user']);
+        $this->assertEquals('h@i', $info['pass']);
     }
 
     public function testEncoding()
     {
         $info = ActiveRecord\Connection::parse_connection_url('mysql://test:test@127.0.0.1/test?charset=utf8');
-        $this->assertEquals('utf8', $info->charset);
+        $this->assertEquals('utf8', $info['charset']);
     }
 }
diff --git a/test/InflectorTest.php b/test/InflectorTest.php
index e8e09a2a..97ba4278 100644
--- a/test/InflectorTest.php
+++ b/test/InflectorTest.php
@@ -1,32 +1,26 @@
 <?php
 
+use ActiveRecord\Inflector;
 use PHPUnit\Framework\TestCase;
 
 require_once __DIR__ . '/../lib/Inflector.php';
 
 class InflectorTest extends TestCase
 {
-    private $inflector;
-
-    public function setUp(): void
-    {
-        $this->inflector = ActiveRecord\Inflector::instance();
-    }
-
     public function testUnderscorify()
     {
-        $this->assertEquals('rm__name__bob', $this->inflector->variablize('rm--name  bob'));
-        $this->assertEquals('One_Two_Three', $this->inflector->underscorify('OneTwoThree'));
+        $this->assertEquals('rm__name__bob', Inflector::variablize('rm--name  bob'));
+        $this->assertEquals('One_Two_Three', Inflector::underscorify('OneTwoThree'));
     }
 
     public function testTableize()
     {
-        $this->assertEquals('angry_people', $this->inflector->tableize('AngryPerson'));
-        $this->assertEquals('my_sqls', $this->inflector->tableize('MySQL'));
+        $this->assertEquals('angry_people', Inflector::tableize('AngryPerson'));
+        $this->assertEquals('my_sqls', Inflector::tableize('MySQL'));
     }
 
     public function testKeyify()
     {
-        $this->assertEquals('building_type_id', $this->inflector->keyify('BuildingType'));
+        $this->assertEquals('building_type_id', Inflector::keyify('BuildingType'));
     }
 }
diff --git a/test/RelationshipTest.php b/test/RelationshipTest.php
index 56375a17..de2f8a11 100644
--- a/test/RelationshipTest.php
+++ b/test/RelationshipTest.php
@@ -552,7 +552,7 @@ public function testHasManyWithExplicitKeys()
 
     public function testHasOneBasic()
     {
-        $this->assert_default_has_one($this->get_relationship());
+        $this->assert_default_has_one(Employee::find(1));
     }
 
     public function testHasOneWithExplicitClassName()
diff --git a/test/SqliteAdapterTest.php b/test/SqliteAdapterTest.php
index f866bc7b..b57758b2 100644
--- a/test/SqliteAdapterTest.php
+++ b/test/SqliteAdapterTest.php
@@ -63,13 +63,13 @@ public function testGh183SqliteadapterAutoincrement()
     public function testDatetimeToString()
     {
         $datetime = '2009-01-01 01:01:01';
-        $this->assertEquals($datetime, $this->connection->datetime_to_string(date_create($datetime)));
+        $this->assertEquals($datetime, $this->connection->datetime_string(date_create($datetime)));
     }
 
     public function testDateToString()
     {
         $datetime = '2009-01-01';
-        $this->assertEquals($datetime, $this->connection->date_to_string(date_create($datetime)));
+        $this->assertEquals($datetime, $this->connection->date_string(date_create($datetime)));
     }
 
     // not supported
diff --git a/test/helpers/AdapterTestCase.php b/test/helpers/AdapterTestCase.php
index 4bdf6f41..0464a0e5 100644
--- a/test/helpers/AdapterTestCase.php
+++ b/test/helpers/AdapterTestCase.php
@@ -397,12 +397,12 @@ public function testQuoteNameDoesNotOverQuote()
     public function testDatetimeToString()
     {
         $datetime = '2009-01-01 01:01:01';
-        $this->assertEquals($datetime, $this->connection->datetime_to_string(date_create($datetime)));
+        $this->assertEquals($datetime, $this->connection->datetime_string(date_create($datetime)));
     }
 
     public function testDateToString()
     {
         $datetime = '2009-01-01';
-        $this->assertEquals($datetime, $this->connection->date_to_string(date_create($datetime)));
+        $this->assertEquals($datetime, $this->connection->date_string(date_create($datetime)));
     }
 }