diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index b667d89..f609de8 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -6,6 +6,7 @@ use Symfony\Component\ClassLoader\ApcUniversalClassLoader;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Symfony\Component\HttpFoundation\Request;
 use Drupal\Core\Language\Language;
+use Drupal\Core\Utility\NestedArray;
 
 /**
  * @file
@@ -2089,28 +2090,7 @@ function drupal_array_merge_deep() {
  * @see drupal_array_merge_deep()
  */
 function drupal_array_merge_deep_array($arrays) {
-  $result = array();
-
-  foreach ($arrays as $array) {
-    foreach ($array as $key => $value) {
-      // Renumber integer keys as array_merge_recursive() does. Note that PHP
-      // automatically converts array keys that are integer strings (e.g., '1')
-      // to integers.
-      if (is_integer($key)) {
-        $result[] = $value;
-      }
-      // Recurse when both values are arrays.
-      elseif (isset($result[$key]) && is_array($result[$key]) && is_array($value)) {
-        $result[$key] = drupal_array_merge_deep_array(array($result[$key], $value));
-      }
-      // Otherwise, use the latter value, overriding any previous value.
-      else {
-        $result[$key] = $value;
-      }
-    }
-  }
-
-  return $result;
+  return NestedArray::mergeDeepArray($arrays);
 }
 
 /**
diff --git a/core/includes/common.inc b/core/includes/common.inc
index f2a4003..ee9620b 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -3,6 +3,7 @@
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 use Drupal\Core\Database\Database;
+use Drupal\Core\Utility\NestedArray;
 
 /**
  * @file
@@ -6373,19 +6374,7 @@ function element_set_attributes(array &$element, array $map) {
  * @see drupal_array_unset_nested_value()
  */
 function &drupal_array_get_nested_value(array &$array, array $parents, &$key_exists = NULL) {
-  $ref = &$array;
-  foreach ($parents as $parent) {
-    if (is_array($ref) && array_key_exists($parent, $ref)) {
-      $ref = &$ref[$parent];
-    }
-    else {
-      $key_exists = FALSE;
-      $null = NULL;
-      return $null;
-    }
-  }
-  $key_exists = TRUE;
-  return $ref;
+  return NestedArray::getValue($array, $parents, $key_exists);
 }
 
 /**
@@ -6450,16 +6439,7 @@ function &drupal_array_get_nested_value(array &$array, array $parents, &$key_exi
  * @see drupal_array_get_nested_value()
  */
 function drupal_array_set_nested_value(array &$array, array $parents, $value, $force = FALSE) {
-  $ref = &$array;
-  foreach ($parents as $parent) {
-    // PHP auto-creates container arrays and NULL entries without error if $ref
-    // is NULL, but throws an error if $ref is set, but not an array.
-    if ($force && isset($ref) && !is_array($ref)) {
-      $ref = array();
-    }
-    $ref = &$ref[$parent];
-  }
-  $ref = $value;
+  NestedArray::setValue($array, $parents, $value, $force);
 }
 
 /**
@@ -6521,15 +6501,7 @@ function drupal_array_set_nested_value(array &$array, array $parents, $value, $f
  * @see drupal_array_get_nested_value()
  */
 function drupal_array_unset_nested_value(array &$array, array $parents, &$key_existed = NULL) {
-  $unset_key = array_pop($parents);
-  $ref = &drupal_array_get_nested_value($array, $parents, $key_existed);
-  if ($key_existed && is_array($ref) && array_key_exists($unset_key, $ref)) {
-    $key_existed = TRUE;
-    unset($ref[$unset_key]);
-  }
-  else {
-    $key_existed = FALSE;
-  }
+  NestedArray::unsetValue($array, $parents, $key_existed);
 }
 
 /**
@@ -6561,11 +6533,7 @@ function drupal_array_unset_nested_value(array &$array, array $parents, &$key_ex
  * @see drupal_array_get_nested_value()
  */
 function drupal_array_nested_key_exists(array $array, array $parents) {
-  // Although this function is similar to PHP's array_key_exists(), its
-  // arguments should be consistent with drupal_array_get_nested_value().
-  $key_exists = NULL;
-  drupal_array_get_nested_value($array, $parents, $key_exists);
-  return $key_exists;
+  return NestedArray::keyExists($array, $parents);
 }
 
 /**
diff --git a/core/lib/Drupal/Core/Config/Config.php b/core/lib/Drupal/Core/Config/Config.php
index a749a4b..1cd8209 100644
--- a/core/lib/Drupal/Core/Config/Config.php
+++ b/core/lib/Drupal/Core/Config/Config.php
@@ -7,6 +7,8 @@
 
 namespace Drupal\Core\Config;
 
+use Drupal\Core\Utility\NestedArray;
+
 /**
  * Defines the default configuration object.
  */
@@ -105,7 +107,7 @@ class Config {
 
     $name = $this->getName();
     if (isset($conf[$name])) {
-      $merged_data = drupal_array_merge_deep($this->data, $conf[$name]);
+      $merged_data = NestedArray::mergeDeepArray(array($this->data, $conf[$name]));
     }
     else {
       $merged_data = $this->data;
@@ -121,7 +123,7 @@ class Config {
       }
       else {
         $key_exists = NULL;
-        $value = drupal_array_get_nested_value($merged_data, $parts, $key_exists);
+        $value = NestedArray::getValue($merged_data, $parts, $key_exists);
         return $key_exists ? $value : NULL;
       }
     }
@@ -157,7 +159,7 @@ class Config {
       $this->data[$key] = $value;
     }
     else {
-      drupal_array_set_nested_value($this->data, $parts, $value);
+      NestedArray::setValue($this->data, $parts, $value);
     }
     return $this;
   }
@@ -213,7 +215,7 @@ class Config {
       unset($this->data[$key]);
     }
     else {
-      drupal_array_unset_nested_value($this->data, $parts);
+      NestedArray::unsetValue($this->data, $parts);
     }
     return $this;
   }
diff --git a/core/lib/Drupal/Core/Utility/NestedArray.php b/core/lib/Drupal/Core/Utility/NestedArray.php
new file mode 100644
index 0000000..58cf283
--- /dev/null
+++ b/core/lib/Drupal/Core/Utility/NestedArray.php
@@ -0,0 +1,341 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\Core\Utility\NestedArray.
+ */
+
+namespace Drupal\Core\Utility;
+
+/**
+ * Provides helpers to perform operations on nested arrays and array keys of variable depth.
+ */
+class NestedArray {
+
+  /**
+   * Retrieves a value from a nested array with variable depth.
+   *
+   * This helper function should be used when the depth of the array element
+   * being retrieved may vary (that is, the number of parent keys is variable).
+   * It is primarily used for form structures and renderable arrays.
+   *
+   * Without this helper function the only way to get a nested array value with
+   * variable depth in one line would be using eval(), which should be avoided:
+   * @code
+   * // Do not do this! Avoid eval().
+   * // May also throw a PHP notice, if the variable array keys do not exist.
+   * eval('$value = $array[\'' . implode("']['", $parents) . "'];");
+   * @endcode
+   *
+   * Instead, use this helper function:
+   * @code
+   * $value = NestedArray::getValue($form, $parents);
+   * @endcode
+   *
+   * The return value will be NULL, regardless of whether the actual value is
+   * NULL or whether the requested key does not exist. If it is required to know
+   * whether the nested array key actually exists, pass a third argument that is
+   * altered by reference:
+   * @code
+   * $key_exists = NULL;
+   * $value = NestedArray::getValue($form, $parents, $key_exists);
+   * if ($key_exists) {
+   *   // ... do something with $value ...
+   * }
+   * @endcode
+   *
+   * However if the number of array parent keys is static, the value should
+   * always be retrieved directly rather than calling this function.
+   * For instance:
+   * @code
+   * $value = $form['signature_settings']['signature'];
+   * @endcode
+   *
+   * @param array $array
+   *   The array from which to get the value.
+   * @param array $parents
+   *   An array of parent keys of the value, starting with the outermost key.
+   * @param bool $key_exists
+   *   (optional) If given, an already defined variable that is altered by
+   *   reference.
+   *
+   * @return mixed
+   *   The requested nested value. Possibly NULL if the value is NULL or not all
+   *   nested parent keys exist. $key_exists is altered by reference and is a
+   *   Boolean that indicates whether all nested parent keys exist (TRUE) or not
+   *   (FALSE). This allows to distinguish between the two possibilities when
+   *   NULL is returned.
+   *
+   * @see NestedArray::setValue()
+   * @see NestedArray::unsetValue()
+   */
+  public static function &getValue(array &$array, array $parents, &$key_exists = NULL) {
+    $ref = &$array;
+    foreach ($parents as $parent) {
+      if (is_array($ref) && array_key_exists($parent, $ref)) {
+        $ref = &$ref[$parent];
+      }
+      else {
+        $key_exists = FALSE;
+        $null = NULL;
+        return $null;
+      }
+    }
+    $key_exists = TRUE;
+    return $ref;
+  }
+
+  /**
+   * Sets a value in a nested array with variable depth.
+   *
+   * This helper function should be used when the depth of the array element you
+   * are changing may vary (that is, the number of parent keys is variable). It
+   * is primarily used for form structures and renderable arrays.
+   *
+   * Example:
+   * @code
+   * // Assume you have a 'signature' element somewhere in a form. It might be:
+   * $form['signature_settings']['signature'] = array(
+   *   '#type' => 'text_format',
+   *   '#title' => t('Signature'),
+   * );
+   * // Or, it might be further nested:
+   * $form['signature_settings']['user']['signature'] = array(
+   *   '#type' => 'text_format',
+   *   '#title' => t('Signature'),
+   * );
+   * @endcode
+   *
+   * To deal with the situation, the code needs to figure out the route to the
+   * element, given an array of parents that is either
+   * @code array('signature_settings', 'signature') @endcode
+   * in the first case or
+   * @code array('signature_settings', 'user', 'signature') @endcode
+   * in the second case.
+   *
+   * Without this helper function the only way to set the signature element in
+   * one line would be using eval(), which should be avoided:
+   * @code
+   * // Do not do this! Avoid eval().
+   * eval('$form[\'' . implode("']['", $parents) . '\'] = $element;');
+   * @endcode
+   *
+   * Instead, use this helper function:
+   * @code
+   * NestedArray::setValue($form, $parents, $element);
+   * @endcode
+   *
+   * However if the number of array parent keys is static, the value should
+   * always be set directly rather than calling this function. For instance,
+   * for the first example we could just do:
+   * @code
+   * $form['signature_settings']['signature'] = $element;
+   * @endcode
+   *
+   * @param array $array
+   *   A reference to the array to modify.
+   * @param array $parents
+   *   An array of parent keys, starting with the outermost key.
+   * @param mixed $value
+   *   The value to set.
+   * @param bool $force
+   *   (optional) If TRUE, the value is forced into the structure even if it
+   *   requires the deletion of an already existing non-array parent value. If
+   *   FALSE, PHP throws an error if trying to add into a value that is not an
+   *   array. Defaults to FALSE.
+   *
+   * @see NestedArray::unsetValue()
+   * @see NestedArray::getValue()
+   */
+  public static function setValue(array &$array, array $parents, $value, $force = FALSE) {
+    $ref = &$array;
+    foreach ($parents as $parent) {
+      // PHP auto-creates container arrays and NULL entries without error if $ref
+      // is NULL, but throws an error if $ref is set, but not an array.
+      if ($force && isset($ref) && !is_array($ref)) {
+        $ref = array();
+      }
+      $ref = &$ref[$parent];
+    }
+    $ref = $value;
+  }
+
+  /**
+   * Unsets a value in a nested array with variable depth.
+   *
+   * This helper function should be used when the depth of the array element you
+   * are changing may vary (that is, the number of parent keys is variable). It
+   * is primarily used for form structures and renderable arrays.
+   *
+   * Example:
+   * @code
+   * // Assume you have a 'signature' element somewhere in a form. It might be:
+   * $form['signature_settings']['signature'] = array(
+   *   '#type' => 'text_format',
+   *   '#title' => t('Signature'),
+   * );
+   * // Or, it might be further nested:
+   * $form['signature_settings']['user']['signature'] = array(
+   *   '#type' => 'text_format',
+   *   '#title' => t('Signature'),
+   * );
+   * @endcode
+   *
+   * To deal with the situation, the code needs to figure out the route to the
+   * element, given an array of parents that is either
+   * @code array('signature_settings', 'signature') @endcode
+   * in the first case or
+   * @code array('signature_settings', 'user', 'signature') @endcode
+   * in the second case.
+   *
+   * Without this helper function the only way to unset the signature element in
+   * one line would be using eval(), which should be avoided:
+   * @code
+   * // Do not do this! Avoid eval().
+   * eval('unset($form[\'' . implode("']['", $parents) . '\']);');
+   * @endcode
+   *
+   * Instead, use this helper function:
+   * @code
+   * NestedArray::unset_nested_value($form, $parents, $element);
+   * @endcode
+   *
+   * However if the number of array parent keys is static, the value should
+   * always be set directly rather than calling this function. For instance, for
+   * the first example we could just do:
+   * @code
+   * unset($form['signature_settings']['signature']);
+   * @endcode
+   *
+   * @param array $array
+   *   A reference to the array to modify.
+   * @param array $parents
+   *   An array of parent keys, starting with the outermost key and including
+   *   the key to be unset.
+   * @param bool $key_existed
+   *   (optional) If given, an already defined variable that is altered by
+   *   reference.
+   *
+   * @see NestedArray::setValue()
+   * @see NestedArray::getValue()
+   */
+  public static function unsetValue(array &$array, array $parents, &$key_existed = NULL) {
+    $unset_key = array_pop($parents);
+    $ref = &self::getValue($array, $parents, $key_existed);
+    if ($key_existed && is_array($ref) && array_key_exists($unset_key, $ref)) {
+      $key_existed = TRUE;
+      unset($ref[$unset_key]);
+    }
+    else {
+      $key_existed = FALSE;
+    }
+  }
+
+  /**
+   * Determines whether a nested array contains the requested keys.
+   *
+   * This helper function should be used when the depth of the array element to
+   * be checked may vary (that is, the number of parent keys is variable). See
+   * NestedArray::setValue() for details. It is primarily used for form
+   * structures and renderable arrays.
+   *
+   * If it is required to also get the value of the checked nested key, use
+   * NestedArray::getValue() instead.
+   *
+   * If the number of array parent keys is static, this helper function is
+   * unnecessary and the following code can be used instead:
+   * @code
+   * $value_exists = isset($form['signature_settings']['signature']);
+   * $key_exists = array_key_exists('signature', $form['signature_settings']);
+   * @endcode
+   *
+   * @param array $array
+   *   The array with the value to check for.
+   * @param array $parents
+   *   An array of parent keys of the value, starting with the outermost key.
+   *
+   * @return bool
+   *   TRUE if all the parent keys exist, FALSE otherwise.
+   *
+   * @see NestedArray::getValue()
+   */
+  public static function keyExists(array $array, array $parents) {
+    // Although this function is similar to PHP's array_key_exists(), its
+    // arguments should be consistent with getValue().
+    $key_exists = NULL;
+    self::getValue($array, $parents, $key_exists);
+    return $key_exists;
+  }
+
+  /**
+   * Merges multiple arrays, recursively, and returns the merged array.
+   *
+   * This function is similar to PHP's array_merge_recursive() function, but it
+   * handles non-array values differently. When merging values that are not both
+   * arrays, the latter value replaces the former rather than merging with it.
+   *
+   * Example:
+   * @code
+   * $link_options_1 = array('fragment' => 'x', 'attributes' => array('title' => t('X'), 'class' => array('a', 'b')));
+   * $link_options_2 = array('fragment' => 'y', 'attributes' => array('title' => t('Y'), 'class' => array('c', 'd')));
+   *
+   * // This results in array('fragment' => array('x', 'y'), 'attributes' => array('title' => array(t('X'), t('Y')), 'class' => array('a', 'b', 'c', 'd'))).
+   * $incorrect = array_merge_recursive($link_options_1, $link_options_2);
+   *
+   * // This results in array('fragment' => 'y', 'attributes' => array('title' => t('Y'), 'class' => array('a', 'b', 'c', 'd'))).
+   * $correct = NestedArray::mergeDeep($link_options_1, $link_options_2);
+   * @endcode
+   *
+   * @param array ...
+   *   Arrays to merge.
+   *
+   * @return array
+   *   The merged array.
+   *
+   * @see NestedArray::mergeDeepArray()
+   */
+  public static function mergeDeep() {
+    return self::mergeDeepArray(func_get_args());
+  }
+
+  /**
+   * Merges multiple arrays, recursively, and returns the merged array.
+   *
+   * This function is equivalent to NestedArray::mergeDeep(), except the
+   * input arrays are passed as a single array parameter rather than a variable
+   * parameter list.
+   *
+   * The following are equivalent:
+   * - NestedArray::mergeDeep($a, $b);
+   * - NestedArray::mergeDeepArray(array($a, $b));
+   *
+   * The following are also equivalent:
+   * - call_user_func_array('NestedArray::mergeDeep', $arrays_to_merge);
+   * - NestedArray::mergeDeepArray($arrays_to_merge);
+   *
+   * @see NestedArray::mergeDeep()
+   */
+  public static function mergeDeepArray(array $arrays) {
+    $result = array();
+    foreach ($arrays as $array) {
+      foreach ($array as $key => $value) {
+        // Renumber integer keys as array_merge_recursive() does. Note that PHP
+        // automatically converts array keys that are integer strings (e.g., '1')
+        // to integers.
+        if (is_integer($key)) {
+          $result[] = $value;
+        }
+        // Recurse when both values are arrays.
+        elseif (isset($result[$key]) && is_array($result[$key]) && is_array($value)) {
+          $result[$key] = self::mergeDeepArray(array($result[$key], $value));
+        }
+        // Otherwise, use the latter value, overriding any previous value.
+        else {
+          $result[$key] = $value;
+        }
+      }
+    }
+    return $result;
+  }
+
+}