Fix hiddenField option not working for radio.

The hiddenField option was not working as documented for radio buttons.
Instead of using the provided value, the hidden input's value was
hardcoded to ''

Refs #11002

lib/Cake/Test/Case/View/Helper/FormHelperTest.php

@@ -4944,6 +4944,30 @@ class FormHelperTest extends CakeTestCase {
 		$this->assertTags($result, $expected);
 	}
 
+/**
+ * test setting a hiddenField value
+ *
+ * @return void
+ */
+	public function testRadioHiddenFieldValue() {
+		$result = $this->Form->input('Model.1.field', array(
+				'type' => 'radio',
+				'options' => array('option A'),
+				'hiddenField' => 'N'
+			)
+		);
+		$expected = array(
+			'div' => array('class' => 'input radio'),
+			array('input' => array('type' => 'hidden', 'name' => 'data[Model][1][field]', 'value' => 'N', 'id' => 'Model1Field_')),
+			array('input' => array('type' => 'radio', 'name' => 'data[Model][1][field]', 'value' => '0', 'id' => 'Model1Field0')),
+			'label' => array('for' => 'Model1Field0'),
+			'option A',
+			'/label',
+			'/div'
+		);
+		$this->assertTags($result, $expected);
+	}
+
 /**
  * test adding an empty option for radio buttons
  *

lib/Cake/View/Helper/FormHelper.php

@@ -1674,7 +1674,7 @@ class FormHelper extends AppHelper {
 				$hidden = $this->hidden($fieldName, array(
 					'form' => isset($attributes['form']) ? $attributes['form'] : null,
 					'id' => $attributes['id'] . '_',
-					'value' => '',
+					'value' => $hiddenField === true ? '' : $hiddenField,
 					'name' => $attributes['name']
 				));
 			}