Fix issue with non-sequential array keys.

Xml::fromArray() should not cause errors with non-sequential
numeric array keys.

Fixes #2580

lib/Cake/Test/Case/Utility/XmlTest.php

@@ -322,6 +322,43 @@ public function testFromArray() {
 		$this->assertEquals(str_replace(array("\r", "\n"), '', $obj->asXML()), $xmlText);
 	}
 
+/**
+ * Test non-sequential keys in list types.
+ *
+ * @return void
+ */
+	public function testFromArrayNonSequentialKeys() {
+		$xmlArray = array(
+			'Event' => array(
+				array(
+					'id' => '235',
+					'Attribute' => array(
+						0 => array(
+							'id' => '9646',
+						),
+						2 => array(
+							'id' => '9647',
+						)
+					)
+				)
+			)
+		);
+		$obj = Xml::fromArray($xmlArray);
+		$expected = <<<XML
+<?xml version="1.0" encoding="UTF-8"?>
+<Event>
+	<id>235</id>
+	<Attribute>
+		<id>9646</id>
+	</Attribute>
+	<Attribute>
+		<id>9647</id>
+	</Attribute>
+</Event>
+XML;
+		$this->assertXmlStringEqualsXmlString($expected, $obj->asXML());
+	}
+
 /**
  * data provider for fromArray() failures
  *

lib/Cake/Utility/Xml.php

@@ -230,7 +230,7 @@ protected static function _fromArray($dom, $node, &$data, $format) {
 					if ($key[0] === '@') {
 						throw new XmlException(__d('cake_dev', 'Invalid array'));
 					}
-					if (array_keys($value) === range(0, count($value) - 1)) { // List
+					if (is_numeric(implode(array_keys($value), ''))) { // List
 						foreach ($value as $item) {
 							$itemData = compact('dom', 'node', 'key', 'format');
 							$itemData['value'] = $item;