diff --git a/core/includes/common.inc b/core/includes/common.inc
index 967a59688ae..2f1474056ad 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -6447,6 +6447,78 @@ function element_set_attributes(array &$element, array $map) {
   }
 }
 
+/**
+ * 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
+ * $value = drupal_array_get_nested_value($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;
+ * $value = drupal_array_get_nested_value($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
+ *   The array from which to get the value.
+ * @param $parents
+ *   An array of parent keys of the value, starting with the outermost key.
+ * @param $key_exists
+ *   (optional) If given, an already defined variable that is altered by
+ *   reference.
+ *
+ * @return
+ *   The requested nested value. Possibly NULL if the value is NULL or not all
+ *   nested parent keys exist. $key_exists is altered by reference and is a
+ *   Boolean that indicates whether all nested parent keys exist (TRUE) or not
+ *   (FALSE). This allows to distinguish between the two possibilities when NULL
+ *   is returned.
+ *
+ * @see drupal_array_set_nested_value()
+ * @see drupal_array_unset_nested_value()
+ */
+function &drupal_array_get_nested_value(array &$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 $ref;
+}
+
 /**
  * Sets a value in a nested array with variable depth.
  *
@@ -6505,6 +6577,7 @@ function element_set_attributes(array &$element, array $map) {
  *   FALSE, PHP throws an error if trying to add into a value that is not an
  *   array. Defaults to FALSE.
  *
+ * @see drupal_array_unset_nested_value()
  * @see drupal_array_get_nested_value()
  */
 function drupal_array_set_nested_value(array &$array, array $parents, $value, $force = FALSE) {
@@ -6521,74 +6594,73 @@ function drupal_array_set_nested_value(array &$array, array $parents, $value, $f
 }
 
 /**
- * Retrieves a value from a nested array with variable depth.
+ * Unsets a value in 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.
+ * 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.
  *
- * 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:
+ * 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:
+ * $form['signature_settings']['user']['signature'] = array(
+ *   '#type' => 'text_format',
+ *   '#title' => t('Signature'),
+ * );
+ * @endcode
+ *
+ * To deal with the situation, the code needs to figure out the route to the
+ * element, given an array of parents that is either
+ * @code array('signature_settings', 'signature') @endcode in the first case or
+ * @code array('signature_settings', 'user', 'signature') @endcode in the second
+ * case.
+ *
+ * Without this helper function the only way to unset the signature element in
+ * one line would be using eval(), which should be avoided:
  * @code
  * // Do not do this! Avoid eval().
- * // May also throw a PHP notice, if the variable array keys do not exist.
- * eval('$value = $array[\'' . implode("']['", $parents) . "'];");
+ * eval('unset($form[\'' . implode("']['", $parents) . '\']);');
  * @endcode
  *
  * Instead, use this helper function:
  * @code
- * $value = drupal_array_get_nested_value($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;
- * $value = drupal_array_get_nested_value($form, $parents, $key_exists);
- * if ($key_exists) {
- *   // ... do something with $value ...
- * }
+ * drupal_array_unset_nested_value($form, $parents, $element);
  * @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:
+ * be set directly rather than calling this function. For instance, for the
+ * first example we could just do:
  * @code
- * $value = $form['signature_settings']['signature'];
+ * unset($form['signature_settings']['signature']);
  * @endcode
  *
  * @param $array
- *   The array from which to get the value.
+ *   A reference to the array to modify.
  * @param $parents
- *   An array of parent keys of the value, starting with the outermost key.
- * @param $key_exists
+ *   An array of parent keys, starting with the outermost key and including the
+ *   key to be unset.
+ * @param $key_existed
  *   (optional) If given, an already defined variable that is altered by
  *   reference.
  *
- * @return
- *   The requested nested value. Possibly NULL if the value is NULL or not all
- *   nested parent keys exist. $key_exists is altered by reference and is a
- *   Boolean that indicates whether all nested parent keys exist (TRUE) or not
- *   (FALSE). This allows to distinguish between the two possibilities when NULL
- *   is returned.
- *
  * @see drupal_array_set_nested_value()
+ * @see drupal_array_get_nested_value()
  */
-function &drupal_array_get_nested_value(array &$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 $null;
-    }
+function drupal_array_unset_nested_value(array &$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;
   }
-  $key_exists = TRUE;
-  return $ref;
 }
 
 /**
diff --git a/core/modules/simpletest/tests/common.test b/core/modules/simpletest/tests/common.test
index 66c0400d0f4..b07ad18bb34 100644
--- a/core/modules/simpletest/tests/common.test
+++ b/core/modules/simpletest/tests/common.test
@@ -2411,6 +2411,118 @@ class DrupalAttributesUnitTest extends DrupalUnitTestCase {
   }
 }
 
+/**
+ * Tests the various drupal_array_* helper functions.
+ */
+class CommonDrupalArrayUnitTest extends DrupalUnitTestCase {
+
+  /**
+   * Form array to check.
+   */
+  protected $form;
+
+  /**
+   * Array of parents for the nested element.
+   */
+  protected $parents;
+
+  public static function getInfo() {
+    return array(
+      'name' => 'drupal_array_*() tests',
+      'description' => 'Tests the various drupal_array_* helper functions.',
+      'group' => 'System',
+    );
+  }
+
+  function setUp() {
+    parent::setUp();
+
+    // Create a form structure with a nested element.
+    $this->form['fieldset']['element'] = array(
+     '#value' => 'Nested element',
+    );
+
+    // Set up parent array.
+    $this->parents = array('fieldset', 'element');
+  }
+
+  /**
+   * Tests getting nested array values.
+   */
+  function testGet() {
+    // Verify getting a value of a nested element.
+    $value = drupal_array_get_nested_value($this->form, $this->parents);
+    $this->assertEqual($value['#value'], 'Nested element', 'Nested element value found.');
+
+    // Verify changing a value of a nested element by reference.
+    $value = &drupal_array_get_nested_value($this->form, $this->parents);
+    $value['#value'] = 'New value';
+    $value = drupal_array_get_nested_value($this->form, $this->parents);
+    $this->assertEqual($value['#value'], 'New value', 'Nested element value was changed by reference.');
+    $this->assertEqual($this->form['fieldset']['element']['#value'], 'New value', 'Nested element value was changed by reference.');
+
+    // Verify that an existing key is reported back.
+    $key_exists = NULL;
+    drupal_array_get_nested_value($this->form, $this->parents, $key_exists);
+    $this->assertIdentical($key_exists, TRUE, 'Existing key found.');
+
+    // Verify that a non-existing key is reported back and throws no errors.
+    $key_exists = NULL;
+    $parents = $this->parents;
+    $parents[] = 'foo';
+    drupal_array_get_nested_value($this->form, $parents, $key_exists);
+    $this->assertIdentical($key_exists, FALSE, 'Non-existing key not found.');
+  }
+
+  /**
+   * Tests setting nested array values.
+   */
+  function testSet() {
+    $new_value = array(
+      '#value' => 'New value',
+      '#required' => TRUE,
+    );
+
+    // Verify setting the value of a nested element.
+    drupal_array_set_nested_value($this->form, $this->parents, $new_value);
+    $this->assertEqual($this->form['fieldset']['element']['#value'], 'New value', 'Changed nested element value found.');
+    $this->assertIdentical($this->form['fieldset']['element']['#required'], TRUE, 'New nested element value found.');
+  }
+
+  /**
+   * Tests unsetting nested array values.
+   */
+  function testUnset() {
+    // Verify unsetting a non-existing nested element throws no errors and the
+    // non-existing key is properly reported.
+    $key_existed = NULL;
+    $parents = $this->parents;
+    $parents[] = 'foo';
+    drupal_array_unset_nested_value($this->form, $parents, $key_existed);
+    $this->assertTrue(isset($this->form['fieldset']['element']['#value']), 'Outermost nested element key still exists.');
+    $this->assertIdentical($key_existed, FALSE, 'Non-existing key not found.');
+
+    // Verify unsetting a nested element.
+    $key_existed = NULL;
+    drupal_array_unset_nested_value($this->form, $this->parents, $key_existed);
+    $this->assertFalse(isset($this->form['fieldset']['element']), 'Removed nested element not found.');
+    $this->assertIdentical($key_existed, TRUE, 'Existing key was found.');
+  }
+
+  /**
+   * Tests existence of array key.
+   */
+  function testKeyExists() {
+    // Verify that existing key is found.
+    $this->assertIdentical(drupal_array_nested_key_exists($this->form, $this->parents), TRUE, 'Nested key found.');
+
+    // Verify that non-existing keys are not found.
+    $parents = $this->parents;
+    $parents[] = 'foo';
+    $this->assertIdentical(drupal_array_nested_key_exists($this->form, $parents), FALSE, 'Non-existing nested key not found.');
+  }
+}
+
 /**
  * Tests converting PHP variables to JSON strings and back.
  */