diff --git a/core/lib/Drupal/Core/Template/Attribute.php b/core/lib/Drupal/Core/Template/Attribute.php
index 1708180..459bb9d 100644
--- a/core/lib/Drupal/Core/Template/Attribute.php
+++ b/core/lib/Drupal/Core/Template/Attribute.php
@@ -6,6 +6,7 @@
  */
 
 namespace Drupal\Core\Template;
+
 use ArrayAccess;
 use IteratorAggregate;
 
@@ -37,20 +38,35 @@ use IteratorAggregate;
  * @see drupal_attributes()
  */
 class Attribute implements ArrayAccess, IteratorAggregate {
+
+  /**
+   * Stores the attribute data.
+   *
+   * @var array
+   */
   protected $storage = array();
 
+  /**
+   * Implements the magic __construct() method.
+   */
   public function __construct($attributes = array()) {
     foreach ($attributes as $name => $value) {
       $this->offsetSet($name, $value);
     }
   }
 
+  /**
+   * Implements ArrayAccess::offsetGet().
+   */
   public function offsetGet($name) {
     if (isset($this->storage[$name])) {
       return $this->storage[$name];
     }
   }
 
+  /**
+   * Implements ArrayAccess::offsetSet().
+   */
   public function offsetSet($name, $value) {
     if (is_array($value)) {
       $value = new AttributeArray($name, $value);
@@ -70,14 +86,23 @@ class Attribute implements ArrayAccess, IteratorAggregate {
     }
   }
 
+  /**
+   * Implements ArrayAccess::offsetUnset().
+   */
   public function offsetUnset($name) {
     unset($this->storage[$name]);
   }
 
+  /**
+   * Implements ArrayAccess::offsetExists().
+   */
   public function offsetExists($name) {
     return isset($this->storage[$name]);
   }
 
+  /**
+   * Implements the magic __toString() method.
+   */
   public function __toString() {
     $return = '';
     foreach ($this->storage as $name => $value) {
@@ -91,6 +116,9 @@ class Attribute implements ArrayAccess, IteratorAggregate {
     return $return;
   }
 
+  /**
+   * Implements the magic __clone() method.
+   */
   public function  __clone() {
     foreach ($this->storage as $name => $value) {
       if (is_object($value)) {
@@ -99,6 +127,9 @@ class Attribute implements ArrayAccess, IteratorAggregate {
     }
   }
 
+  /**
+   * Implements IteratorAggregate::getIterator().
+   */
   public function getIterator() {
     return new ArrayIterator($this->storage);
   }
@@ -109,4 +140,5 @@ class Attribute implements ArrayAccess, IteratorAggregate {
   public function value() {
     return $this->value;
   }
+
 }
diff --git a/core/lib/Drupal/Core/Template/AttributeArray.php b/core/lib/Drupal/Core/Template/AttributeArray.php
index b6dc889..d4f8771 100644
--- a/core/lib/Drupal/Core/Template/AttributeArray.php
+++ b/core/lib/Drupal/Core/Template/AttributeArray.php
@@ -5,6 +5,11 @@
  * Definition of Drupal\Core\Template\AttributeArray.
  */
 
+namespace Drupal\Core\Template;
+
+use ArrayAccess;
+use IteratorAggregate;
+
 /**
  * A class that defines a type of Attribute that can be added to as an array.
  *
@@ -23,15 +28,18 @@
  *
  * @see Drupal\Core\Template\Attribute
  */
-namespace Drupal\Core\Template;
-use ArrayAccess;
-use IteratorAggregate;
-
 class AttributeArray extends AttributeValueBase implements ArrayAccess, IteratorAggregate {
+
+  /**
+   * Implements ArrayAccess::offsetGet().
+   */
   public function offsetGet($offset) {
     return $this->value[$offset];
   }
 
+  /**
+   * Implements ArrayAccess::offsetSet().
+   */
   public function offsetSet($offset, $value) {
     if (isset($offset)) {
       $this->value[$offset] = $value;
@@ -41,19 +49,31 @@ class AttributeArray extends AttributeValueBase implements ArrayAccess, Iterator
     }
   }
 
+  /**
+   * Implements ArrayAccess::offsetUnset().
+   */
   public function offsetUnset($offset) {
     unset($this->value[$offset]);
   }
 
+  /**
+   * Implements ArrayAccess::offsetExists().
+   */
   public function offsetExists($offset) {
     return isset($this->value[$offset]);
   }
 
+  /**
+   * Implements the magic __toString() method.
+   */
   public function __toString() {
     $this->printed = TRUE;
     return implode(' ', array_map('check_plain', $this->value));
   }
 
+  /**
+   * Implements IteratorAggregate::getIterator().
+   */
   public function getIterator() {
     return new ArrayIterator($this->value);
   }
@@ -64,4 +84,5 @@ class AttributeArray extends AttributeValueBase implements ArrayAccess, Iterator
   public function value() {
     return $this->value;
   }
+
 }
diff --git a/core/lib/Drupal/Core/Template/AttributeBoolean.php b/core/lib/Drupal/Core/Template/AttributeBoolean.php
index 8886ff5..48ca388 100644
--- a/core/lib/Drupal/Core/Template/AttributeBoolean.php
+++ b/core/lib/Drupal/Core/Template/AttributeBoolean.php
@@ -28,11 +28,20 @@ namespace Drupal\Core\Template;
  * @see Drupal\Core\Template\Attribute
  */
 class AttributeBoolean extends AttributeValueBase {
+
+  /**
+   * Overrides AttributeValueBase::render().
+   */
   public function render() {
     return $this->__toString();
   }
+
+  /**
+   * Implements the magic __toString() method.
+   */
   public function __toString() {
     $this->printed = TRUE;
     return $this->value === FALSE ? '' : check_plain($this->name);
   }
+
 }
diff --git a/core/lib/Drupal/Core/Template/AttributeString.php b/core/lib/Drupal/Core/Template/AttributeString.php
index cee327a..9776467 100644
--- a/core/lib/Drupal/Core/Template/AttributeString.php
+++ b/core/lib/Drupal/Core/Template/AttributeString.php
@@ -23,8 +23,13 @@ namespace Drupal\Core\Template;
  * @see Drupal\Core\Template\Attribute
  */
 class AttributeString extends AttributeValueBase {
+
+  /**
+   * Implements the magic __toString() method.
+   */
   public function __toString() {
     $this->printed = TRUE;
     return check_plain($this->value);
   }
+
 }
diff --git a/core/lib/Drupal/Core/Template/AttributeValueBase.php b/core/lib/Drupal/Core/Template/AttributeValueBase.php
index 4b04f4a..e54a1e5 100644
--- a/core/lib/Drupal/Core/Template/AttributeValueBase.php
+++ b/core/lib/Drupal/Core/Template/AttributeValueBase.php
@@ -13,8 +13,31 @@ namespace Drupal\Core\Template;
  * @see Drupal\Core\Template\Attribute
  */
 abstract class AttributeValueBase {
-  protected $printed = FALSE, $value, $name;
 
+  /**
+   * Whether this attribute hsa been printed already.
+   *
+   * @var bool
+   */
+  protected $printed = FALSE;
+
+  /**
+   * The value itself.
+   *
+   * @var mixed
+   */
+  protected $value;
+
+  /**
+   * The name of the value.
+   *
+   * @var mixed
+   */
+  protected $name;
+
+  /**
+   * Implements the magic __construct() method.
+   */
   public function __construct($name, $value) {
     $this->name = $name;
     $this->value = $value;
@@ -26,7 +49,7 @@ abstract class AttributeValueBase {
    * While __toString only returns the value in a string form, render()
    * contains the name of the attribute as well.
    *
-   * @return
+   * @return string
    *   The string representation of the attribute.
    */
   public function render() {
@@ -36,11 +59,16 @@ abstract class AttributeValueBase {
   /**
    * Whether this attribute hsa been printed already.
    *
-   * @return
+   * @return bool
    *   TRUE if this attribute has been printed, FALSE otherwise.
    */
   public function printed() {
     return $this->printed;
   }
+
+  /**
+   * Implements the magic __toString() method.
+   */
   abstract function __toString();
+
 }