diff --git a/src/ResultSet/AbstractResultSet.php b/src/ResultSet/AbstractResultSet.php
index 3911885e38..a147baecb4 100644
--- a/src/ResultSet/AbstractResultSet.php
+++ b/src/ResultSet/AbstractResultSet.php
@@ -25,26 +25,18 @@ abstract class AbstractResultSet implements Iterator, ResultSetInterface
      * if array, already buffering
      * @var mixed
      */
-    protected $buffer = null;
+    protected $buffer;
 
-    /**
-     * @var null|int
-     */
-    protected $count = null;
+    /** @var null|int */
+    protected $count;
 
-    /**
-     * @var Iterator|IteratorAggregate|ResultInterface
-     */
-    protected $dataSource = null;
+    /** @var Iterator|IteratorAggregate|ResultInterface */
+    protected $dataSource;
 
-    /**
-     * @var int
-     */
+    /** @var int */
     protected $fieldCount = 0;
 
-    /**
-     * @var int
-     */
+    /** @var int */
     protected $position = 0;
 
     /**
@@ -54,7 +46,7 @@ abstract class AbstractResultSet implements Iterator, ResultSetInterface
      * @return self Provides a fluent interface
      * @throws Exception\InvalidArgumentException
      */
-    public function initialize($dataSource)
+    public function initialize($dataSource) : self
     {
         // reset buffering
         if (is_array($this->buffer)) {
@@ -93,42 +85,33 @@ public function initialize($dataSource)
         return $this;
     }
 
-    /**
-     * @return self Provides a fluent interface
-     * @throws Exception\RuntimeException
-     */
-    public function buffer()
+    public function buffer() : self
     {
         if ($this->buffer === -2) {
             throw new Exception\RuntimeException('Buffering must be enabled before iteration is started');
-        } elseif ($this->buffer === null) {
+        }
+
+        if ($this->buffer === null) {
             $this->buffer = [];
             if ($this->dataSource instanceof ResultInterface) {
                 $this->dataSource->rewind();
             }
         }
+
         return $this;
     }
 
-    public function isBuffered()
+    public function isBuffered() : bool
     {
-        if ($this->buffer === -1 || is_array($this->buffer)) {
-            return true;
-        }
-        return false;
+        return $this->buffer === -1 || is_array($this->buffer);
     }
 
-    /**
-     * Get the data source used to create the result set
-     *
-     * @return null|Iterator
-     */
-    public function getDataSource()
+    public function getDataSource() : ?Iterator
     {
         return $this->dataSource;
     }
 
-    public function getFieldCount(): int
+    public function getFieldCount() : int
     {
         if (null !== $this->fieldCount) {
             return $this->fieldCount;
@@ -155,12 +138,7 @@ public function getFieldCount(): int
         return $this->fieldCount;
     }
 
-    /**
-     * Iterator: move pointer to next item
-     *
-     * @return void
-     */
-    public function next()
+    public function next() : void
     {
         if ($this->buffer === null) {
             $this->buffer = -2; // implicitly disable buffering from here on
@@ -171,12 +149,7 @@ public function next()
         $this->position++;
     }
 
-    /**
-     * Iterator: retrieve current key
-     *
-     * @return mixed
-     */
-    public function key()
+    public function key() : int
     {
         return $this->position;
     }
@@ -205,30 +178,21 @@ public function current()
         return is_array($data) ? $data : null;
     }
 
-    /**
-     * Iterator: is pointer valid?
-     *
-     * @return bool
-     */
-    public function valid()
+    public function valid() : bool
     {
         if (is_array($this->buffer) && isset($this->buffer[$this->position])) {
             return true;
         }
+
         if ($this->dataSource instanceof Iterator) {
             return $this->dataSource->valid();
-        } else {
-            $key = key($this->dataSource);
-            return ($key !== null);
         }
+
+        $key = key($this->dataSource);
+        return ($key !== null);
     }
 
-    /**
-     * Iterator: rewind
-     *
-     * @return void
-     */
-    public function rewind()
+    public function rewind() : void
     {
         if (! is_array($this->buffer)) {
             if ($this->dataSource instanceof Iterator) {
@@ -240,12 +204,7 @@ public function rewind()
         $this->position = 0;
     }
 
-    /**
-     * Countable: return count of rows
-     *
-     * @return int
-     */
-    public function count()
+    public function count() : int
     {
         if ($this->count !== null) {
             return $this->count;
@@ -264,7 +223,7 @@ public function count()
      * @return array
      * @throws Exception\RuntimeException if any row is not castable to an array
      */
-    public function toArray()
+    public function toArray() : array
     {
         $return = [];
         foreach ($this as $row) {
diff --git a/src/ResultSet/Exception/ExceptionInterface.php b/src/ResultSet/Exception/ExceptionInterface.php
index 646aec4c88..6276bc40f1 100644
--- a/src/ResultSet/Exception/ExceptionInterface.php
+++ b/src/ResultSet/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\ResultSet\Exception;
 
 use Zend\Db\Exception;
diff --git a/src/ResultSet/Exception/InvalidArgumentException.php b/src/ResultSet/Exception/InvalidArgumentException.php
index 00d376146d..91156cd252 100644
--- a/src/ResultSet/Exception/InvalidArgumentException.php
+++ b/src/ResultSet/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\ResultSet\Exception;
 
 use Zend\Db\Exception;
diff --git a/src/ResultSet/Exception/RuntimeException.php b/src/ResultSet/Exception/RuntimeException.php
index cd46b497b7..9b3d54fa52 100644
--- a/src/ResultSet/Exception/RuntimeException.php
+++ b/src/ResultSet/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\ResultSet\Exception;
 
 use Zend\Db\Exception;
diff --git a/src/ResultSet/HydratingResultSet.php b/src/ResultSet/HydratingResultSet.php
index a30d4f5793..4d0c2ffa2c 100644
--- a/src/ResultSet/HydratingResultSet.php
+++ b/src/ResultSet/HydratingResultSet.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\ResultSet;
 
 use ArrayObject;
@@ -16,77 +16,39 @@
 
 class HydratingResultSet extends AbstractResultSet
 {
-    /**
-     * @var HydratorInterface
-     */
-    protected $hydrator = null;
+    /** @var HydratorInterface */
+    protected $hydrator;
 
-    /**
-     * @var null|object
-     */
-    protected $objectPrototype = null;
+    /** @var null|object */
+    protected $objectPrototype;
 
-    /**
-     * Constructor
-     *
-     * @param  null|HydratorInterface $hydrator
-     * @param  null|object $objectPrototype
-     */
-    public function __construct(HydratorInterface $hydrator = null, $objectPrototype = null)
+    public function __construct(?HydratorInterface $hydrator = null, ?object $objectPrototype = null)
     {
         $defaultHydratorClass = class_exists(ArraySerializableHydrator::class)
             ? ArraySerializableHydrator::class
             : ArraySerializable::class;
         $this->setHydrator($hydrator ?: new $defaultHydratorClass());
-        $this->setObjectPrototype(($objectPrototype) ?: new ArrayObject);
+        $this->setObjectPrototype($objectPrototype ?: new ArrayObject);
     }
 
-    /**
-     * Set the row object prototype
-     *
-     * @param  object $objectPrototype
-     * @return self Provides a fluent interface
-     * @throws Exception\InvalidArgumentException
-     */
-    public function setObjectPrototype($objectPrototype)
+    public function setObjectPrototype(object $objectPrototype) : self
     {
-        if (! is_object($objectPrototype)) {
-            throw new Exception\InvalidArgumentException(
-                'An object must be set as the object prototype, a ' . gettype($objectPrototype) . ' was provided.'
-            );
-        }
         $this->objectPrototype = $objectPrototype;
         return $this;
     }
 
-    /**
-     * Get the row object prototype
-     *
-     * @return object
-     */
-    public function getObjectPrototype()
+    public function getObjectPrototype() : object
     {
         return $this->objectPrototype;
     }
 
-    /**
-     * Set the hydrator to use for each row object
-     *
-     * @param HydratorInterface $hydrator
-     * @return self Provides a fluent interface
-     */
-    public function setHydrator(HydratorInterface $hydrator)
+    public function setHydrator(HydratorInterface $hydrator) : self
     {
         $this->hydrator = $hydrator;
         return $this;
     }
 
-    /**
-     * Get the hydrator to use for each row object
-     *
-     * @return HydratorInterface
-     */
-    public function getHydrator()
+    public function getHydrator() : HydratorInterface
     {
         return $this->hydrator;
     }
@@ -94,7 +56,7 @@ public function getHydrator()
     /**
      * Iterator: get current item
      *
-     * @return object
+     * @return null|array|bool
      */
     public function current()
     {
@@ -113,13 +75,7 @@ public function current()
         return $object;
     }
 
-    /**
-     * Cast result set to array of arrays
-     *
-     * @return array
-     * @throws Exception\RuntimeException if any row is not castable to an array
-     */
-    public function toArray()
+    public function toArray() : array
     {
         $return = [];
         foreach ($this as $row) {
diff --git a/src/ResultSet/ResultSet.php b/src/ResultSet/ResultSet.php
index ebbb455c3b..f7a5d897e7 100644
--- a/src/ResultSet/ResultSet.php
+++ b/src/ResultSet/ResultSet.php
@@ -1,50 +1,37 @@
 <?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\ResultSet;
 
 use ArrayObject;
 
 class ResultSet extends AbstractResultSet
 {
-    const TYPE_ARRAYOBJECT = 'arrayobject';
-    const TYPE_ARRAY  = 'array';
+    public const TYPE_ARRAYOBJECT = 'arrayobject';
+    public const TYPE_ARRAY  = 'array';
 
-    /**
-     * Allowed return types
-     *
-     * @var array
-     */
     protected $allowedReturnTypes = [
         self::TYPE_ARRAYOBJECT,
         self::TYPE_ARRAY,
     ];
 
-    /**
-     * @var ArrayObject
-     */
-    protected $arrayObjectPrototype = null;
+    /** @var ArrayObject */
+    protected $arrayObjectPrototype;
 
     /**
      * Return type to use when returning an object from the set
      *
-     * @var ResultSet::TYPE_ARRAYOBJECT|ResultSet::TYPE_ARRAY
+     * @var string One of the above declared TYPE constants
      */
     protected $returnType = self::TYPE_ARRAYOBJECT;
 
-    /**
-     * Constructor
-     *
-     * @param string           $returnType
-     * @param null|ArrayObject $arrayObjectPrototype
-     */
-    public function __construct($returnType = self::TYPE_ARRAYOBJECT, $arrayObjectPrototype = null)
+    public function __construct(string $returnType = self::TYPE_ARRAYOBJECT, ?ArrayObject $arrayObjectPrototype = null)
     {
         if (in_array($returnType, [self::TYPE_ARRAY, self::TYPE_ARRAYOBJECT])) {
             $this->returnType = $returnType;
@@ -52,24 +39,14 @@ public function __construct($returnType = self::TYPE_ARRAYOBJECT, $arrayObjectPr
             $this->returnType = self::TYPE_ARRAYOBJECT;
         }
         if ($this->returnType === self::TYPE_ARRAYOBJECT) {
-            $this->setArrayObjectPrototype(($arrayObjectPrototype) ?: new ArrayObject([], ArrayObject::ARRAY_AS_PROPS));
+            $this->setArrayObjectPrototype($arrayObjectPrototype ?: new ArrayObject([], ArrayObject::ARRAY_AS_PROPS));
         }
     }
 
-    /**
-     * Set the row object prototype
-     *
-     * @param  ArrayObject $arrayObjectPrototype
-     * @return self Provides a fluent interface
-     * @throws Exception\InvalidArgumentException
-     */
-    public function setArrayObjectPrototype($arrayObjectPrototype)
+    public function setArrayObjectPrototype(object $arrayObjectPrototype) : self
     {
-        if (! is_object($arrayObjectPrototype)
-            || (
-                ! $arrayObjectPrototype instanceof ArrayObject
-                && ! method_exists($arrayObjectPrototype, 'exchangeArray')
-            )
+        if (! $arrayObjectPrototype instanceof ArrayObject
+            && ! method_exists($arrayObjectPrototype, 'exchangeArray')
         ) {
             throw new Exception\InvalidArgumentException(
                 'Object must be of type ArrayObject, or at least implement exchangeArray'
@@ -79,28 +56,18 @@ public function setArrayObjectPrototype($arrayObjectPrototype)
         return $this;
     }
 
-    /**
-     * Get the row object prototype
-     *
-     * @return ArrayObject
-     */
-    public function getArrayObjectPrototype()
+    public function getArrayObjectPrototype() : ArrayObject
     {
         return $this->arrayObjectPrototype;
     }
 
-    /**
-     * Get the return type to use when returning objects from the set
-     *
-     * @return string
-     */
-    public function getReturnType()
+    public function getReturnType() : string
     {
         return $this->returnType;
     }
 
     /**
-     * @return array|\ArrayObject|null
+     * @return array|ArrayObject|null
      */
     public function current()
     {
diff --git a/src/ResultSet/ResultSetInterface.php b/src/ResultSet/ResultSetInterface.php
index 5891dbfc27..3474d6816f 100644
--- a/src/ResultSet/ResultSetInterface.php
+++ b/src/ResultSet/ResultSetInterface.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\ResultSet;
 
 use Countable;