diff --git a/3.0.0.md b/3.0.0.md
index b1c3abfb90..c48427557f 100644
--- a/3.0.0.md
+++ b/3.0.0.md
@@ -28,3 +28,7 @@ Changed `setDriver(DriverInterface $driver)` for all the following platforms:
     - Zend\Db\Adapter\Platform\Postgresql
     - Zend\Db\Adapter\Platform\Sqlite
     - Zend\Db\Adapter\Platform\SqlServer
+
+- Zend\Db\RowGateway\AbstractRowGateway
+
+We cannot use type hint for parameter in `offsetExists()` because of definition in `\ArrayAccess` 
diff --git a/src/RowGateway/AbstractRowGateway.php b/src/RowGateway/AbstractRowGateway.php
index 89b2068fff..746252bf8b 100644
--- a/src/RowGateway/AbstractRowGateway.php
+++ b/src/RowGateway/AbstractRowGateway.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\RowGateway;
 
 use ArrayAccess;
@@ -16,40 +16,26 @@
 
 abstract class AbstractRowGateway implements ArrayAccess, Countable, RowGatewayInterface
 {
-    /**
-     * @var bool
-     */
+    /** @var bool */
     protected $isInitialized = false;
 
-    /**
-     * @var string|TableIdentifier
-     */
-    protected $table = null;
+    /** @var string|TableIdentifier */
+    protected $table;
 
-    /**
-     * @var array
-     */
-    protected $primaryKeyColumn = null;
+    /** @var array */
+    protected $primaryKeyColumn = [];
 
-    /**
-     * @var array
-     */
-    protected $primaryKeyData = null;
+    /** @var array */
+    protected $primaryKeyData = [];
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $data = [];
 
-    /**
-     * @var Sql
-     */
-    protected $sql = null;
+    /** @var Sql */
+    protected $sql;
 
-    /**
-     * @var Feature\FeatureSet
-     */
-    protected $featureSet = null;
+    /** @var Feature\FeatureSet */
+    protected $featureSet;
 
     /**
      * initialize()
@@ -71,12 +57,14 @@ public function initialize()
             throw new Exception\RuntimeException('This row object does not have a valid table set.');
         }
 
-        if ($this->primaryKeyColumn === null) {
-            throw new Exception\RuntimeException('This row object does not have a primary key column set.');
-        } elseif (is_string($this->primaryKeyColumn)) {
+        if (is_string($this->primaryKeyColumn)) {
             $this->primaryKeyColumn = (array) $this->primaryKeyColumn;
         }
 
+        if (count($this->primaryKeyColumn) === 0) {
+            throw new Exception\RuntimeException('This row object does not have a primary key column set.');
+        }
+
         if (! $this->sql instanceof Sql) {
             throw new Exception\RuntimeException('This row object does not have a Sql object set.');
         }
@@ -86,42 +74,26 @@ public function initialize()
         $this->isInitialized = true;
     }
 
-    /**
-     * Populate Data
-     *
-     * @param  array $rowData
-     * @param  bool  $rowExistsInDatabase
-     * @return self Provides a fluent interface
-     */
-    public function populate(array $rowData, $rowExistsInDatabase = false)
+    public function populate(array $rowData, bool $rowExistsInDatabase = false) : self
     {
         $this->initialize();
 
         $this->data = $rowData;
-        if ($rowExistsInDatabase == true) {
+        if ($rowExistsInDatabase === true) {
             $this->processPrimaryKeyData();
         } else {
-            $this->primaryKeyData = null;
+            $this->primaryKeyData = [];
         }
 
         return $this;
     }
 
-    /**
-     * @param mixed $array
-     * @return AbstractRowGateway
-     */
-    public function exchangeArray($array)
+    public function exchangeArray(array $array) : self
     {
         return $this->populate($array, true);
     }
 
-    /**
-     * Save
-     *
-     * @return int
-     */
-    public function save()
+    public function save() : int
     {
         $this->initialize();
 
@@ -163,7 +135,7 @@ public function save()
             $statement = $this->sql->prepareStatementForSqlObject($insert);
 
             $result = $statement->execute();
-            if (($primaryKeyValue = $result->getGeneratedValue()) && count($this->primaryKeyColumn) == 1) {
+            if (($primaryKeyValue = $result->getGeneratedValue()) && count($this->primaryKeyColumn) === 1) {
                 $this->primaryKeyData = [$this->primaryKeyColumn[0] => $primaryKeyValue];
             } else {
                 // make primary key data available so that $where can be complete
@@ -192,12 +164,7 @@ public function save()
         return $rowsAffected;
     }
 
-    /**
-     * Delete
-     *
-     * @return int
-     */
-    public function delete()
+    public function delete() : int
     {
         $this->initialize();
 
@@ -213,9 +180,9 @@ public function delete()
         $result = $statement->execute();
 
         $affectedRows = $result->getAffectedRows();
-        if ($affectedRows == 1) {
+        if ($affectedRows === 1) {
             // detach from database
-            $this->primaryKeyData = null;
+            $this->primaryKeyData = [];
         }
 
         return $affectedRows;
@@ -227,7 +194,7 @@ public function delete()
      * @param  string $offset
      * @return bool
      */
-    public function offsetExists($offset)
+    public function offsetExists($offset) : bool
     {
         return array_key_exists($offset, $this->data);
     }
@@ -250,7 +217,7 @@ public function offsetGet($offset)
      * @param  mixed $value
      * @return self Provides a fluent interface
      */
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value) : self
     {
         $this->data[$offset] = $value;
         return $this;
@@ -262,92 +229,52 @@ public function offsetSet($offset, $value)
      * @param  string $offset
      * @return self Provides a fluent interface
      */
-    public function offsetUnset($offset)
+    public function offsetUnset($offset) : self
     {
         $this->data[$offset] = null;
         return $this;
     }
 
-    /**
-     * @return int
-     */
-    public function count()
+    public function count() : int
     {
         return count($this->data);
     }
 
-    /**
-     * To array
-     *
-     * @return array
-     */
-    public function toArray()
+    public function toArray() : array
     {
         return $this->data;
     }
 
-    /**
-     * __get
-     *
-     * @param  string $name
-     * @throws Exception\InvalidArgumentException
-     * @return mixed
-     */
-    public function __get($name)
+    public function __get(string $name)
     {
         if (array_key_exists($name, $this->data)) {
             return $this->data[$name];
-        } else {
-            throw new Exception\InvalidArgumentException('Not a valid column in this row: ' . $name);
         }
+
+        throw new Exception\InvalidArgumentException('Not a valid column in this row: ' . $name);
     }
 
-    /**
-     * __set
-     *
-     * @param  string $name
-     * @param  mixed $value
-     * @return void
-     */
-    public function __set($name, $value)
+    public function __set(string $name, $value) : void
     {
         $this->offsetSet($name, $value);
     }
 
-    /**
-     * __isset
-     *
-     * @param  string $name
-     * @return bool
-     */
-    public function __isset($name)
+    public function __isset(string $name) : bool
     {
         return $this->offsetExists($name);
     }
 
-    /**
-     * __unset
-     *
-     * @param  string $name
-     * @return void
-     */
-    public function __unset($name)
+    public function __unset(string $name) : void
     {
         $this->offsetUnset($name);
     }
 
-    /**
-     * @return bool
-     */
-    public function rowExistsInDatabase()
+    public function rowExistsInDatabase() : bool
     {
-        return ($this->primaryKeyData !== null);
+        return count($this->primaryKeyData) > 0;
     }
 
-    /**
-     * @throws Exception\RuntimeException
-     */
-    protected function processPrimaryKeyData()
+    protected function processPrimaryKeyData() : void
     {
         $this->primaryKeyData = [];
         foreach ($this->primaryKeyColumn as $column) {
diff --git a/src/RowGateway/Exception/ExceptionInterface.php b/src/RowGateway/Exception/ExceptionInterface.php
index b3d11b4a67..7b912d3ba5 100644
--- a/src/RowGateway/Exception/ExceptionInterface.php
+++ b/src/RowGateway/Exception/ExceptionInterface.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\RowGateway\Exception;
 
 use Zend\Db\Exception;
diff --git a/src/RowGateway/Exception/InvalidArgumentException.php b/src/RowGateway/Exception/InvalidArgumentException.php
index 4b34d35377..6f08007c36 100644
--- a/src/RowGateway/Exception/InvalidArgumentException.php
+++ b/src/RowGateway/Exception/InvalidArgumentException.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\RowGateway\Exception;
 
 use Zend\Db\Exception;
diff --git a/src/RowGateway/Exception/RuntimeException.php b/src/RowGateway/Exception/RuntimeException.php
index 6e53975b7d..eabc0cb2b7 100644
--- a/src/RowGateway/Exception/RuntimeException.php
+++ b/src/RowGateway/Exception/RuntimeException.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\RowGateway\Exception;
 
 use Zend\Db\Exception;
diff --git a/src/RowGateway/Feature/AbstractFeature.php b/src/RowGateway/Feature/AbstractFeature.php
index 9ff69c57ad..b9359b9ca3 100644
--- a/src/RowGateway/Feature/AbstractFeature.php
+++ b/src/RowGateway/Feature/AbstractFeature.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\RowGateway\Feature;
 
 use Zend\Db\RowGateway\AbstractRowGateway;
@@ -14,44 +14,31 @@
 
 abstract class AbstractFeature extends AbstractRowGateway
 {
-    /**
-     * @var AbstractRowGateway
-     */
-    protected $rowGateway = null;
+    /** @var AbstractRowGateway */
+    protected $rowGateway;
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $sharedData = [];
 
     /**
-     * @return string
+     * @return string|bool
      */
     public function getName()
     {
         return get_class($this);
     }
 
-    /**
-     * @param AbstractRowGateway $rowGateway
-     */
-    public function setRowGateway(AbstractRowGateway $rowGateway)
+    public function setRowGateway(AbstractRowGateway $rowGateway) : void
     {
         $this->rowGateway = $rowGateway;
     }
 
-    /**
-     * @throws \Zend\Db\RowGateway\Exception\RuntimeException
-     */
     public function initialize()
     {
         throw new Exception\RuntimeException('This method is not intended to be called on this object.');
     }
 
-    /**
-     * @return array
-     */
-    public function getMagicMethodSpecifications()
+    public function getMagicMethodSpecifications() : array
     {
         return [];
     }
diff --git a/src/RowGateway/Feature/FeatureSet.php b/src/RowGateway/Feature/FeatureSet.php
index f3c36a07c3..0c8d413288 100644
--- a/src/RowGateway/Feature/FeatureSet.php
+++ b/src/RowGateway/Feature/FeatureSet.php
@@ -1,50 +1,35 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\RowGateway\Feature;
 
 use Zend\Db\RowGateway\AbstractRowGateway;
 
 class FeatureSet
 {
-    const APPLY_HALT = 'halt';
+    public const APPLY_HALT = 'halt';
 
-    /**
-     * @var AbstractRowGateway
-     */
-    protected $rowGateway = null;
+    /** @var AbstractRowGateway */
+    protected $rowGateway;
 
-    /**
-     * @var AbstractFeature[]
-     */
+    /** @var AbstractFeature[] */
     protected $features = [];
 
-    /**
-     * @var array
-     */
+    /** @var array */
     protected $magicSpecifications = [];
 
-    /**
-     * @param array $features
-     */
     public function __construct(array $features = [])
     {
-        if ($features) {
-            $this->addFeatures($features);
-        }
+        $this->addFeatures($features);
     }
 
-    /**
-     * @param AbstractRowGateway $rowGateway
-     * @return self Provides a fluent interface
-     */
-    public function setRowGateway(AbstractRowGateway $rowGateway)
+    public function setRowGateway(AbstractRowGateway $rowGateway) : self
     {
         $this->rowGateway = $rowGateway;
         foreach ($this->features as $feature) {
@@ -53,6 +38,10 @@ public function setRowGateway(AbstractRowGateway $rowGateway)
         return $this;
     }
 
+    /**
+     * @param mixed $featureClassName
+     * @return bool|AbstractFeature
+     */
     public function getFeatureByClassName($featureClassName)
     {
         $feature = false;
@@ -65,11 +54,7 @@ public function getFeatureByClassName($featureClassName)
         return $feature;
     }
 
-    /**
-     * @param array $features
-     * @return self Provides a fluent interface
-     */
-    public function addFeatures(array $features)
+    public function addFeatures(array $features) : self
     {
         foreach ($features as $feature) {
             $this->addFeature($feature);
@@ -77,18 +62,14 @@ public function addFeatures(array $features)
         return $this;
     }
 
-    /**
-     * @param AbstractFeature $feature
-     * @return self Provides a fluent interface
-     */
-    public function addFeature(AbstractFeature $feature)
+    public function addFeature(AbstractFeature $feature) : self
     {
         $this->features[] = $feature;
         $feature->setRowGateway($feature);
         return $this;
     }
 
-    public function apply($method, $args)
+    public function apply(string $method, array $args) : void
     {
         foreach ($this->features as $feature) {
             if (method_exists($feature, $method)) {
@@ -100,62 +81,30 @@ public function apply($method, $args)
         }
     }
 
-    /**
-     * @param string $property
-     * @return bool
-     */
-    public function canCallMagicGet($property)
+    public function canCallMagicGet(string $property) : bool
     {
         return false;
     }
 
-    /**
-     * @param string $property
-     * @return mixed
-     */
-    public function callMagicGet($property)
+    public function callMagicGet(string $property) : void
     {
-        $return = null;
-        return $return;
     }
 
-    /**
-     * @param string $property
-     * @return bool
-     */
-    public function canCallMagicSet($property)
+    public function canCallMagicSet(string $property) : bool
     {
         return false;
     }
 
-    /**
-     * @param $property
-     * @param $value
-     * @return mixed
-     */
-    public function callMagicSet($property, $value)
+    public function callMagicSet(string $property, $value) : void
     {
-        $return = null;
-        return $return;
     }
 
-    /**
-     * @param string $method
-     * @return bool
-     */
-    public function canCallMagicCall($method)
+    public function canCallMagicCall(string $method) : bool
     {
         return false;
     }
 
-    /**
-     * @param string $method
-     * @param array $arguments
-     * @return mixed
-     */
-    public function callMagicCall($method, $arguments)
+    public function callMagicCall(string $method, array $arguments) : void
     {
-        $return = null;
-        return $return;
     }
 }
diff --git a/src/RowGateway/RowGateway.php b/src/RowGateway/RowGateway.php
index 2248538eab..a014e6d790 100644
--- a/src/RowGateway/RowGateway.php
+++ b/src/RowGateway/RowGateway.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\RowGateway;
 
 use Zend\Db\Adapter\Adapter;
@@ -19,18 +19,15 @@ class RowGateway extends AbstractRowGateway
      *
      * @param string $primaryKeyColumn
      * @param string|\Zend\Db\Sql\TableIdentifier $table
-     * @param Adapter|Sql $adapterOrSql
+     * @param null|Adapter|Sql $adapterOrSql
      * @throws Exception\InvalidArgumentException
      */
-    public function __construct($primaryKeyColumn, $table, $adapterOrSql = null)
+    public function __construct(string $primaryKeyColumn, $table, $adapterOrSql = null)
     {
-        // setup primary key
-        $this->primaryKeyColumn = empty($primaryKeyColumn) ? null : (array) $primaryKeyColumn;
+        $this->primaryKeyColumn = $primaryKeyColumn === '' ? [] : (array) $primaryKeyColumn;
 
-        // set table
         $this->table = $table;
 
-        // set Sql object
         if ($adapterOrSql instanceof Sql) {
             $this->sql = $adapterOrSql;
         } elseif ($adapterOrSql instanceof Adapter) {
diff --git a/src/RowGateway/RowGatewayInterface.php b/src/RowGateway/RowGatewayInterface.php
index b623c4ed72..c6be38d2de 100644
--- a/src/RowGateway/RowGatewayInterface.php
+++ b/src/RowGateway/RowGatewayInterface.php
@@ -1,12 +1,12 @@
 <?php
 /**
- * Zend Framework (http://framework.zend.com/)
- *
- * @link      http://github.com/zendframework/zf2 for the canonical source repository
- * @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
- * @license   http://framework.zend.com/license/new-bsd New BSD License
+ * @see       https://github.com/zendframework/zend-db for the canonical source repository
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-db/blob/master/LICENSE.md New BSD License
  */
 
+declare(strict_types=1);
+
 namespace Zend\Db\RowGateway;
 
 interface RowGatewayInterface