Fix postLink() & postButton() with nested data.

Flatten deeply nested array data before generating hidden inputs.
This solves 'Array to string conversion' errors.

Closes #2894

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

@@ -7431,6 +7431,25 @@ class FormHelperTest extends CakeTestCase {
 	}
 
 /**
+ * Test using postButton with N dimensional data.
+ *
+ * @return void
+ */
+	public function testPostButtonNestedData() {
+		$data = array(
+			'one' => array(
+				'two' => array(
+					3, 4, 5
+				)
+			)
+		);
+		$result = $this->Form->postButton('Send', '/', array('data' => $data));
+		$this->assertContains('<input type="hidden" name="data[one][two][0]" value="3"', $result);
+		$this->assertContains('<input type="hidden" name="data[one][two][1]" value="4"', $result);
+		$this->assertContains('<input type="hidden" name="data[one][two][2]" value="5"', $result);
+	}
+
+/**
  * Test that postButton adds _Token fields.
  *
  * @return void
@@ -7552,6 +7571,25 @@ class FormHelperTest extends CakeTestCase {
 	}
 
 /**
+ * Test using postLink with N dimensional data.
+ *
+ * @return void
+ */
+	public function testPostLinkNestedData() {
+		$data = array(
+			'one' => array(
+				'two' => array(
+					3, 4, 5
+				)
+			)
+		);
+		$result = $this->Form->postLink('Send', '/', array('data' => $data));
+		$this->assertContains('<input type="hidden" name="data[one][two][0]" value="3"', $result);
+		$this->assertContains('<input type="hidden" name="data[one][two][1]" value="4"', $result);
+		$this->assertContains('<input type="hidden" name="data[one][two][2]" value="5"', $result);
+	}
+
+/**
  * test creating postLinks after a GET form.
  *
  * @return void

lib/Cake/View/Helper/FormHelper.php

@@ -1715,7 +1715,7 @@ class FormHelper extends AppHelper {
 	public function postButton($title, $url, $options = array()) {
 		$out = $this->create(false, array('id' => false, 'url' => $url));
 		if (isset($options['data']) && is_array($options['data'])) {
-			foreach ($options['data'] as $key => $value) {
+			foreach (Hash::flatten($options['data']) as $key => $value) {
 				$out .= $this->hidden($key, array('value' => $value, 'id' => false));
 			}
 			unset($options['data']);
@@ -1779,7 +1779,7 @@ class FormHelper extends AppHelper {
 
 		$fields = array();
 		if (isset($options['data']) && is_array($options['data'])) {
-			foreach ($options['data'] as $key => $value) {
+			foreach (Hash::flatten($options['data']) as $key => $value) {
 				$fields[$key] = $value;
 				$out .= $this->hidden($key, array('value' => $value, 'id' => false));
 			}